wifi: mt76: mt7925: fix locking in mt7925_change_vif_links()

wifi: mt76: mt7925: fix locking in mt7925_change_vif_links()

&dev->mt76.mutex lock is taken using mt792x_mutex_acquire(dev) but not
released in one of the error paths, add the unlock to fix it.

Fixes: 5cd0bd815c8a ("wifi: mt76: mt7925: fix NULL deref check in mt7925_change_vif_links")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202503031055.3ZRqxhAl-lkp@intel.com/
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://patch.msgid.link/20250727140416.1153406-1-harshit.m.mogalapalli@oracle.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>