nvme-core: do not pass empty queue_limits to blk_mq_alloc_queue()

In nvme_alloc_admin_tag_set(), an empty queue_limits struct is
currently allocated on the stack and passed by reference to
blk_mq_alloc_queue().

This is redundant because blk_mq_alloc_queue() already handles
a NULL limits pointer by internally substituting it with a default
empty queue_limits struct.
Remove the unnecessary local variable and pass a NULL value.

Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: maurizio-lombardi

drivers/nvme/host/core.c

@@ -4834,7 +4834,6 @@ EXPORT_SYMBOL_GPL(nvme_complete_async_event);
 int nvme_alloc_admin_tag_set(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set,
 		const struct blk_mq_ops *ops, unsigned int cmd_size)
 {
-	struct queue_limits lim = {};
 	int ret;
 
 	memset(set, 0, sizeof(*set));
@@ -4861,7 +4860,7 @@ int nvme_alloc_admin_tag_set(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set,
 	if (ctrl->admin_q)
 		blk_put_queue(ctrl->admin_q);
 
-	ctrl->admin_q = blk_mq_alloc_queue(set, &lim, NULL);
+	ctrl->admin_q = blk_mq_alloc_queue(set, NULL, NULL);
 	if (IS_ERR(ctrl->admin_q)) {
 		ret = PTR_ERR(ctrl->admin_q);
 		goto out_free_tagset;