bpf: Fix divide-by-zero in btf_struct_walk()

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "kernel/bpf/btf.c"
                    ],
                    "versions": [
                        {
                            "version": "9c5f8a1008a121e4c6b24af211034e24b0b63081",
                            "lessThan": "1ea3820937f8022e044c41c6e95c84b02741b45f",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "9c5f8a1008a121e4c6b24af211034e24b0b63081",
                            "lessThan": "172756f02663ad45c889c001c1a8cb4082a01a05",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "9c5f8a1008a121e4c6b24af211034e24b0b63081",
                            "lessThan": "934e9ba9f8d05656a48624710be67ca4dc8482e6",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "9c5f8a1008a121e4c6b24af211034e24b0b63081",
                            "lessThan": "63af086cb5fa6f72fd924f86bea4c2194da663a2",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "9c5f8a1008a121e4c6b24af211034e24b0b63081",
                            "lessThan": "8eb4cd72daad3a9ee63d2281bbdd16ce6d9406b1",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "9c5f8a1008a121e4c6b24af211034e24b0b63081",
                            "lessThan": "b8fa56722e9c43bcd59c51fe4c7edd5f4158a11b",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "9c5f8a1008a121e4c6b24af211034e24b0b63081",
                            "lessThan": "b0b3dc66529676228cb938cbcad66920f735c223",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "kernel/bpf/btf.c"
                    ],
                    "versions": [
                        {
                            "version": "5.8",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "5.8",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.222",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.189",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.158",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.112",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.55",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2.9",
                            "lessThanOrEqual": "7.2.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.3",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }