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>
diff --git a/block/blk.h b/block/blk.h
index c37492f..74444c4 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -39,14 +39,9 @@
 static inline struct blk_flush_queue *blk_get_flush_queue(
 		struct request_queue *q, struct blk_mq_ctx *ctx)
 {
-	struct blk_mq_hw_ctx *hctx;
-
-	if (!q->mq_ops)
-		return q->fq;
-
-	hctx = q->mq_ops->map_queue(q, ctx->cpu);
-
-	return hctx->fq;
+	if (q->mq_ops)
+		return blk_mq_map_queue(q, ctx->cpu)->fq;
+	return q->fq;
 }
 
 static inline void __blk_get_queue(struct request_queue *q)