iscsi-scst: Fix performance regression

A recent change in iscsi_threads_pool_get changed 2 from being the
minimum count to the maximum.  Rectify.

Author: bmeagherix

iscsi-scst/kernel/iscsi.c

@@ -4108,7 +4108,7 @@ int iscsi_threads_pool_get(bool dedicated, const cpumask_t *cpu_mask,
 	if (dedicated) {
 		count = 1;
 	} else if (!cpu_mask) {
-		count = blk_mq_num_online_queues(2);
+		count = max_t(int, blk_mq_num_online_queues(0), 2);
 	} else {
 		count = 0;
 		for_each_cpu(i, cpu_mask)