btrfs: switch extent_buffer spinning_writers from atomic to int

The spinning_writers is either 0 or 1 and always updated under the lock,
so we don't need the atomic_t semantics.

Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/print-tree.c

@@ -157,7 +157,7 @@ static void print_eb_refs_lock(struct extent_buffer *eb)
 		   atomic_read(&eb->read_locks),
 		   eb->blocking_writers,
 		   atomic_read(&eb->blocking_readers),
-		   atomic_read(&eb->spinning_writers),
+		   eb->spinning_writers,
 		   atomic_read(&eb->spinning_readers),
 		   eb->lock_owner, current->pid);
 #endif