wifi: mt76: mt7925: fix crash in reset link replay

In the Linux kernel, the following vulnerability has been resolved: wifi: mt76: mt7925: fix crash in reset link replay During reset recovery, mt7925_vif_connect_iter() replays firmware state for links tracked in mvif->valid_links. After MLO link changes or MCU timeout recovery, the driver bitmap can temporarily contain a link whose mac80211 bss_conf has already gone away. This can pass a NULL bss_conf to mt76_connac_mcu_uni_add_dev(), matching the crash where x1, the second argument, is NULL: pc : mt76_connac_mcu_uni_add_dev+0x8c/0x1f8 [mt76_connac_lib] lr : mt7925_vif_connect_iter+0x9c/0x168 [mt7925_common] x2 : ffffff80a77f6018 x1 : 0000000000000000 x0 : ffffff8099402080 Call trace: mt76_connac_mcu_uni_add_dev+0x8c/0x1f8 [mt76_connac_lib] mt7925_vif_connect_iter+0x9c/0x168 [mt7925_common] mt7925_mac_reset_work+0x264/0x2f8 [mt7925_common] Skip missing bss_conf entries before replaying the link. Non-MLO AP/STA reset replay is unchanged because the helper still returns &vif->bss_conf for the legacy link.