Btrfs: remove unused argument of btrfs_extend_item()

Argument 'trans' is not used in btrfs_extend_item().

Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index ea14ecb..769eb86 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -841,7 +841,7 @@
 		diff /= csum_size;
 		diff *= csum_size;
 
-		btrfs_extend_item(trans, root, path, diff);
+		btrfs_extend_item(root, path, diff);
 		goto csum;
 	}