xfs: kill the unused XFS_QMOPT_* flush flags V2

dquots are never flushed asynchronously. Remove the flag and the
async write support from the flush function. Make the default flush
a delwri flush to make the inode flush code, which leaves the
XFS_QMOPT_SYNC the only flag remaining.  Convert that to use
SYNC_WAIT instead, just like the inode flush code.

V2:
- just pass flush flags straight through

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

fs/xfs/xfs_quota.h

@@ -222,16 +222,10 @@ typedef struct xfs_qoff_logformat {
 #define XFS_QMOPT_DELRTBCOUNT	0x0400000
 #define XFS_QMOPT_RES_INOS	0x0800000
 
-/*
- * flags for dqflush and dqflush_all.
- */
-#define XFS_QMOPT_SYNC		0x1000000
-#define XFS_QMOPT_DELWRI	0x4000000
-
 /*
  * flags for dqalloc.
  */
-#define XFS_QMOPT_INHERIT	0x8000000
+#define XFS_QMOPT_INHERIT	0x1000000
 
 /*
  * flags to xfs_trans_mod_dquot.