btrfs: mark some local function as 'static'

Cc: Josef Bacik <jbacik@fusionio.com>
Cc: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index ea8d522..579efcc 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -837,7 +837,7 @@
  * them in one of two extent_io trees.  This is used to make sure all of
  * those extents are on disk for transaction or log commit
  */
-int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
+static int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
 				struct extent_io_tree *dirty_pages, int mark)
 {
 	int ret;