xfs: get rid of indirections in the quotaops implementation

Currently we call from the nicely abstracted linux quotaops into a ugly
multiplexer just to split the calls out at the same boundary again.
Rewrite the quota ops handling to remove that obfucation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
index 5f6de1e..04f058c 100644
--- a/fs/xfs/linux-2.6/xfs_sync.h
+++ b/fs/xfs/linux-2.6/xfs_sync.h
@@ -19,6 +19,7 @@
 #define XFS_SYNC_H 1
 
 struct xfs_mount;
+struct xfs_perag;
 
 typedef struct bhv_vfs_sync_work {
 	struct list_head	w_list;