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 <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/exynos-cpufreq.c

···
 	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",