cpuidle: lpm-levels: Correctly check for list empty

Correctly check for list empty condition to get least cluster
latency.

Change-Id: I56f11e4a80c24d337ee231f6d0bc461a90f1a2ea
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>

Author: mkshahc

drivers/cpuidle/lpm-levels.c

@@ -159,7 +159,7 @@ static uint32_t least_cluster_latency(struct lpm_cluster *cluster,
 	uint32_t latency = 0;
 	int i;
 
-	if (!cluster->list.next) {
+	if (list_empty(&cluster->list)) {
 		for (i = 0; i < cluster->nlevels; i++) {
 			level = &cluster->levels[i];
 			pwr_params = &level->pwr;