blk-mq: Reorder fields in 'struct blk_mq_tag_set'

Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size of 'struct blk_mq_tag_set'
from 304 to 296 bytes.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/6f249f9b02a3490283ef0278096556de41aa0cf0.1676626130.git.christophe.jaillet@wanadoo.frSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/blk-mq.h

@@ -473,6 +473,7 @@ enum hctx_type {
 
 /**
  * struct blk_mq_tag_set - tag set that can be shared between request queues
+ * @ops:	   Pointers to functions that implement block driver behavior.
  * @map:	   One or more ctx -> hctx mappings. One map exists for each
  *		   hardware queue type (enum hctx_type) that the driver wishes
  *		   to support. There are no restrictions on maps being of the
@@ -480,7 +481,6 @@ enum hctx_type {
  *		   types.
  * @nr_maps:	   Number of elements in the @map array. A number in the range
  *		   [1, HCTX_MAX_TYPES].
- * @ops:	   Pointers to functions that implement block driver behavior.
  * @nr_hw_queues:  Number of hardware queues supported by the block driver that
  *		   owns this data structure.
  * @queue_depth:   Number of tags per hardware queue, reserved tags included.
@@ -505,9 +505,9 @@ enum hctx_type {
  *		   (BLK_MQ_F_BLOCKING).
  */
 struct blk_mq_tag_set {
+	const struct blk_mq_ops	*ops;
 	struct blk_mq_queue_map	map[HCTX_MAX_TYPES];
 	unsigned int		nr_maps;
-	const struct blk_mq_ops	*ops;
 	unsigned int		nr_hw_queues;
 	unsigned int		queue_depth;
 	unsigned int		reserved_tags;