net: bridge: mcast: properly convert mglist to rcu

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/bridge/br_multicast.c"
                    ],
                    "versions": [
                        {
                            "version": "07f8ac4a1e26e8283542cdaf658a6e2a12fd6980",
                            "lessThan": "37cb9a81600da8250f24e25edc07253b62353cbe",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "07f8ac4a1e26e8283542cdaf658a6e2a12fd6980",
                            "lessThan": "98247c8264d2076f81fa114bdfa2c2271953ac7c",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "07f8ac4a1e26e8283542cdaf658a6e2a12fd6980",
                            "lessThan": "38ab2a435001a3c4dbeb70a52f5921e1ccd66f55",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "07f8ac4a1e26e8283542cdaf658a6e2a12fd6980",
                            "lessThan": "f7bf57e94a5d6214b87be08486cb33836fbfa573",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "07f8ac4a1e26e8283542cdaf658a6e2a12fd6980",
                            "lessThan": "4b772869a1e5f9da5cef5b9c722ec0aa424ee0a0",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/bridge/br_multicast.c"
                    ],
                    "versions": [
                        {
                            "version": "3.16",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "3.16",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.158",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.111",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.53",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2.7",
                            "lessThanOrEqual": "7.2.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.3",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }