rtc: cpcap: convert to devm_rtc_allocate_device

This allows further improvement of the driver.

Link: https://lore.kernel.org/r/20200306015703.42101-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-cpcap.c

@@ -256,12 +256,12 @@ static int cpcap_rtc_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	platform_set_drvdata(pdev, rtc);
-	rtc->rtc_dev = devm_rtc_device_register(dev, "cpcap_rtc",
-						&cpcap_rtc_ops, THIS_MODULE);
-
+	rtc->rtc_dev = devm_rtc_allocate_device(dev);
 	if (IS_ERR(rtc->rtc_dev))
 		return PTR_ERR(rtc->rtc_dev);
 
+	rtc->rtc_dev->ops = &cpcap_rtc_ops;
+
 	err = cpcap_get_vendor(dev, rtc->regmap, &rtc->vendor);
 	if (err)
 		return err;
@@ -298,7 +298,7 @@ static int cpcap_rtc_probe(struct platform_device *pdev)
 		/* ignore error and continue without wakeup support */
 	}
 
-	return 0;
+	return rtc_register_device(rtc->rtc_dev);
 }
 
 static const struct of_device_id cpcap_rtc_of_match[] = {