block: Use accessor functions for queue limits

Convert all external users of queue limits to using wrapper functions
instead of poking the request queue variables directly.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-map.c b/block/blk-map.c
index ef2492a..9083cf0 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -115,7 +115,7 @@
 	struct bio *bio = NULL;
 	int ret;
 
-	if (len > (q->max_hw_sectors << 9))
+	if (len > (queue_max_hw_sectors(q) << 9))
 		return -EINVAL;
 	if (!len)
 		return -EINVAL;
@@ -292,7 +292,7 @@
 	struct bio *bio;
 	int ret;
 
-	if (len > (q->max_hw_sectors << 9))
+	if (len > (queue_max_hw_sectors(q) << 9))
 		return -EINVAL;
 	if (!len || !kbuf)
 		return -EINVAL;