xfs: fix static and extern sparse warnings

The kbuild test robot indicated that there were some new sparse
warnings in fs/xfs/xfs_dquot_buf.c. Actually, there were a lot more
that is wasn't warning about, so fix them all up.

Reported-by: kbuild test robot
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 4eb63ad..d971f49 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1155,7 +1155,7 @@
  * Note: xfs_log_quiesce() stops background log work - the callers must ensure
  * it is started again when appropriate.
  */
-void
+static void
 xfs_quiesce_attr(
 	struct xfs_mount	*mp)
 {