mmc_block: indicate strict ordering

The MMC block driver services requests one at a time and in strict
order. Indicate this to the block layer so that it can handle barriers
in an efficient manner.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/card/queue.c

@@ -131,6 +131,7 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card, spinlock_t *lock
 	mq->req = NULL;
 
 	blk_queue_prep_rq(mq->queue, mmc_prep_request);
+	blk_queue_ordered(mq->queue, QUEUE_ORDERED_DRAIN, NULL);
 
 #ifdef CONFIG_MMC_BLOCK_BOUNCE
 	if (host->max_hw_segs == 1) {