[media] tm6000: Fix mutex unbalance

Hi

Fix never unlocked mutex. No more crash after removing USB stick.

With my best regards, Dmitry.
Signed-off-by: NBeholder Intl. Ltd. Dmitry Belimov <d.belimov@gmail.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/tm6000/tm6000-core.c

@@ -722,5 +722,5 @@ void tm6000_close_extension(struct tm6000_core *dev)
 				ops->fini(dev);
 		}
 	}
-	mutex_lock(&tm6000_devlist_mutex);
+	mutex_unlock(&tm6000_devlist_mutex);
 }