btrfs: remove redundant code from btrfs_free_stale_devices

Following the refactor of btrfs_free_stale_devices in
7bcb8164 ("btrfs: use device_list_mutex when removing stale devices")
fs_devices are freed after they have been iterated by the inner
list_for_each so the use-after-free fixed by introducing the break in
fd649f10 ("btrfs: Fix use-after-free when cleaning up fs_devs with
a single stale device") is no longer necessary. Just remove it
altogether. No functional changes.
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -595,8 +595,6 @@ static int btrfs_free_stale_devices(const char *path,
 			btrfs_free_device(device);
 
 			ret = 0;
-			if (fs_devices->num_devices == 0)
-				break;
 		}
 		mutex_unlock(&fs_devices->device_list_mutex);