btrfs: move file-item prototypes into their own header

Move these prototypes out of ctree.h and into file-item.h.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 8500472..9c10019 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -33,6 +33,7 @@
 #include "fs.h"
 #include "accessors.h"
 #include "extent-tree.h"
+#include "file-item.h"
 
 /* simple helper to fault in pages and copy.  This should go away
  * and be replaced with calls into generic code.