drivers/rtc: Replace PTR_RET with PTR_ERR_OR_ZERO

PTR_RET is now deprecated. Use PTR_ERR_OR_ZERO instead.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/rtc/rtc-m48t35.c b/drivers/rtc/rtc-m48t35.c
index 23c3779..411adb3 100644
--- a/drivers/rtc/rtc-m48t35.c
+++ b/drivers/rtc/rtc-m48t35.c
@@ -175,7 +175,7 @@
 
 	priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35",
 				  &m48t35_ops, THIS_MODULE);
-	return PTR_RET(priv->rtc);
+	return PTR_ERR_OR_ZERO(priv->rtc);
 }
 
 static struct platform_driver m48t35_platform_driver = {