blk-mq: remove ->map_queue

All drivers use the default, so provide an inline version of it.  If we
ever need other queue mapping we can add an optional method back,
although supporting will also require major changes to the queue setup
code.

This provides better code generation, and better debugability as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/md/dm-rq.c

@@ -908,7 +908,6 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
 
 static struct blk_mq_ops dm_mq_ops = {
 	.queue_rq = dm_mq_queue_rq,
-	.map_queue = blk_mq_map_queue,
 	.complete = dm_softirq_done,
 	.init_request = dm_mq_init_request,
 };