btrfs: make functions static when possible

Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index c60197b..a36c87db 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -74,8 +74,8 @@
  * retake all the spinlocks in the path.  You can safely use NULL
  * for held
  */
-noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
-					struct extent_buffer *held)
+static noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
+					       struct extent_buffer *held)
 {
 	int i;