exynos-cpufreq: fix false return check from "regulator_set_voltage"

Currently, code checks false return value from "regulator_set_voltage"
to show failure message. Modify the code to check proper return
value from "regulator_set_voltage".

Signed-off-by: Manish Badarkhe <badarkhe.manish@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/exynos-cpufreq.c

@@ -135,7 +135,7 @@ post_notify:
 	if ((freqs.new < freqs.old) ||
 	   ((freqs.new > freqs.old) && safe_arm_volt)) {
 		/* down the voltage after frequency change */
-		regulator_set_voltage(arm_regulator, arm_volt,
+		ret = regulator_set_voltage(arm_regulator, arm_volt,
 				arm_volt);
 		if (ret) {
 			pr_err("%s: failed to set cpu voltage to %d\n",