Btrfs: make things static and include the right headers

Shut up various sparse warnings about symbols that should be either
static or have their declarations in scope.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/btrfs/inode-item.c b/fs/btrfs/inode-item.c
index d93451c..3d46fa1 100644
--- a/fs/btrfs/inode-item.c
+++ b/fs/btrfs/inode-item.c
@@ -20,7 +20,7 @@
 #include "disk-io.h"
 #include "transaction.h"
 
-int find_name_in_backref(struct btrfs_path *path, const char * name,
+static int find_name_in_backref(struct btrfs_path *path, const char *name,
 			 int name_len, struct btrfs_inode_ref **ref_ret)
 {
 	struct extent_buffer *leaf;