mptcp: Initialise rcv_mss before calling tcp_send_active_reset() in mptcp_do_fastclose().

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/mptcp/protocol.c"
                    ],
                    "versions": [
                        {
                            "version": "9ea05fabce31ff93a0adae8221c58bc6d7b832f3",
                            "lessThan": "46b8b58f93f1b383c3840fc6e8fab6c3bce9295f",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "3a13454fd098ed51e733958488f8ec62859a9ed8",
                            "lessThan": "eee39f83246a81d970a9ecb7392b7ab74e660094",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "f6fb2cbc91a81178dea23d463503b4525a76825d",
                            "lessThan": "05f5e26d488cdc7abc2a826cf1071782d5a21203",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "c4f7b0916b95fd2226e5ab98882482b08f52e1c0",
                            "lessThan": "88163f85d59b4164884df900ee171720fd26686b",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "ae155060247be8dcae3802a95bd1bdf93ab3215d",
                            "lessThan": "f07f4ea53e22429c84b20832fa098b5ecc0d4e35",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/mptcp/protocol.c"
                    ],
                    "versions": [
                        {
                            "version": "6.1.159",
                            "lessThan": "6.1.160",
                            "status": "affected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.119",
                            "lessThan": "6.6.120",
                            "status": "affected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.60",
                            "lessThan": "6.12.61",
                            "status": "affected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.17.10",
                            "lessThan": "6.17.11",
                            "status": "affected",
                            "versionType": "semver"
                        }
                    ]
                }