btrfs: add separate helper for unlock_extent_cached with GFP_ATOMIC

There's only one instance where we pass different gfp mask to
unlock_extent_cached. Add a separate helper for that and then we can
drop the gfp parameter from unlock_extent_cached.

Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c405914..8780945 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2493,7 +2493,7 @@ endio_readpage_release_extent(struct extent_io_tree *tree, u64 start, u64 len,
 
 	if (uptodate && tree->track_uptodate)
 		set_extent_uptodate(tree, start, end, &cached, GFP_ATOMIC);
-	unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
+	unlock_extent_cached_atomic(tree, start, end, &cached);
 }
 
 /*