xfs: remove explicit xfs_sync_data/xfs_sync_attr calls on umount

On the final put of a superblock the VFS already calls sync_filesystem
for us to write out all data and wait for it.  No need to start another
asynchronous writeback inside ->put_super.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 0283b88..66cefb2 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -308,7 +308,7 @@
 /*
  * Write out pagecache data for the whole filesystem.
  */
-int
+STATIC int
 xfs_sync_data(
 	struct xfs_mount	*mp,
 	int			flags)
@@ -329,7 +329,7 @@
 /*
  * Write out inode metadata (attributes) for the whole filesystem.
  */
-int
+STATIC int
 xfs_sync_attr(
 	struct xfs_mount	*mp,
 	int			flags)