memory: samsung: exynos5422-dmc: Reduce protected code area in IRQ handler

Speed-up a bit this IRQ processing as there is no need to protect
return value or printing.

Signed-off-by: Bernard Zhao <[e-mail]>
Acked-by: Lukasz Luba <[e-mail]>
Signed-off-by: Krzysztof Kozlowski <[e-mail]>

drivers/memory/samsung/exynos5422-dmc.c

···
 	struct exynos5_dmc *dmc = priv;
 
 	mutex_lock(&dmc->df->lock);
-
 	exynos5_dmc_perf_events_check(dmc);
-
 	res = update_devfreq(dmc->df);
+	mutex_unlock(&dmc->df->lock);
+
 	if (res)
 		dev_warn(dmc->dev, "devfreq failed with %d\n", res);
-
-	mutex_unlock(&dmc->df->lock);
 
 	return IRQ_HANDLED;
 }