wifi: mt76: mt7921: fix potential deadlock in mt7921_roc_abort_sync

In the Linux kernel, the following vulnerability has been resolved: wifi: mt76: mt7921: fix potential deadlock in mt7921_roc_abort_sync roc_abort_sync() can deadlock with roc_work(). roc_work() holds dev->mt76.mutex, while cancel_work_sync() waits for roc_work() to finish. If the caller already owns the same mutex, both sides block and no progress is possible. This deadlock can occur during station removal when mt76_sta_state() -> mt76_sta_remove() -> mt7921_mac_sta_remove() -> mt7921_roc_abort_sync() invokes cancel_work_sync() while roc_work() is still running and holding dev->mt76.mutex. This avoids the mutex deadlock and preserves exactly-once work ownership.