xfs: put in missed fix for merge problem

I intended to do this as part of fixing part of the conflict with
the merge with Linus' tree, but evidently it didn't get included in
the commit.

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_trans_ail.c

@@ -434,7 +434,7 @@ xfsaild_push(
 
 			if (!IOP_PUSHBUF(lip)) {
 				stuck++;
-				flush_log = 1;
+				ailp->xa_log_flush++;
 			} else {
 				ailp->xa_last_pushed_lsn = lsn;
 			}