bcache: fix variable length array abuse in btree_iter

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/md/bcache/bset.c",
                        "drivers/md/bcache/bset.h",
                        "drivers/md/bcache/btree.c",
                        "drivers/md/bcache/super.c",
                        "drivers/md/bcache/sysfs.c",
                        "drivers/md/bcache/writeback.c"
                    ],
                    "versions": [
                        {
                            "version": "cafe563591446cf80bfbc2fe3bc72a2e36cf1060",
                            "lessThan": "2c3d7b03b658dc8bfa6112b194b67b92a87e081b",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "cafe563591446cf80bfbc2fe3bc72a2e36cf1060",
                            "lessThan": "5a1922adc5798b7ec894cd3f197afb6f9591b023",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "cafe563591446cf80bfbc2fe3bc72a2e36cf1060",
                            "lessThan": "934e1e4331859183a861f396d7dfaf33cb5afb02",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "cafe563591446cf80bfbc2fe3bc72a2e36cf1060",
                            "lessThan": "6479b9f41583b013041943c4602e1ad61cec8148",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "cafe563591446cf80bfbc2fe3bc72a2e36cf1060",
                            "lessThan": "0c31344e22dd8d6b1394c6e4c41d639015bdc671",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "cafe563591446cf80bfbc2fe3bc72a2e36cf1060",
                            "lessThan": "3a861560ccb35f2a4f0a4b8207fa7c2a35fc7f31",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/md/bcache/bset.c",
                        "drivers/md/bcache/bset.h",
                        "drivers/md/bcache/btree.c",
                        "drivers/md/bcache/super.c",
                        "drivers/md/bcache/sysfs.c",
                        "drivers/md/bcache/writeback.c"
                    ],
                    "versions": [
                        {
                            "version": "3.10",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "3.10",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.10.221",
                            "lessThanOrEqual": "5.10.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.162",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.94",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.34",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.9.5",
                            "lessThanOrEqual": "6.9.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.10",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }