Btrfs: fix page cache memory leak

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
index 22519b8..32de1ea 100644
--- a/fs/btrfs/hash.c
+++ b/fs/btrfs/hash.c
@@ -11,6 +11,7 @@
  */
 
 #include <linux/types.h>
+#include "hash.h"
 #define DELTA 0x9E3779B9
 
 static void TEA_transform(__u32 buf[2], __u32 const in[])