xfs: merge xfs_ag.h into xfs_format.h

More on-disk format consolidation.  A few declarations that weren't on-disk
format related move into better suitable spots.

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

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 24b4ebe..b0a594e 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -34,10 +34,10 @@
 #include <linux/backing-dev.h>
 #include <linux/freezer.h>
 
+#include "xfs_format.h"
 #include "xfs_log_format.h"
 #include "xfs_trans_resv.h"
 #include "xfs_sb.h"
-#include "xfs_ag.h"
 #include "xfs_mount.h"
 #include "xfs_trace.h"
 #include "xfs_log.h"