PM / devfreq: mediatek: unlock on error in mtk_ccifreq_target()

Call mutex_unlock(&drv->reg_lock) before returning the error code.

Link: https://lore.kernel.org/all/1bada9b2-d276-4123-bfdf-03d165569543@moroto.mountain/
Fixes: d2805601 ("PM / devfreq: mediatek: protect oop in critical session")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/devfreq/mtk-cci-devfreq.c

@@ -146,7 +146,8 @@ static int mtk_ccifreq_target(struct device *dev, unsigned long *freq,
 	opp = devfreq_recommended_opp(dev, &opp_rate, 1);
 	if (IS_ERR(opp)) {
 		dev_err(dev, "failed to find opp for freq: %ld\n", opp_rate);
-		return PTR_ERR(opp);
+		ret = PTR_ERR(opp);
+		goto out_unlock;
 	}
 
 	voltage = dev_pm_opp_get_voltage(opp);