rtc: pcf85063: return meaningful value for RTC_VL_READ

PCF85063_REG_SC_OS means the voltage dropped too low and data has been
lost.

Link: https://lore.kernel.org/r/20191214220259.621996-12-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-pcf85063.c

@@ -289,15 +289,9 @@ static int pcf85063_ioctl(struct device *dev, unsigned int cmd,
 		if (ret < 0)
 			return ret;
 
-		if (status & PCF85063_REG_SC_OS)
-			dev_warn(&pcf85063->rtc->dev, "Voltage low, data loss detected.\n");
+		status = status & PCF85063_REG_SC_OS ? RTC_VL_DATA_INVALID : 0;
 
-		status &= PCF85063_REG_SC_OS;
-
-		if (copy_to_user((void __user *)arg, &status, sizeof(int)))
-			return -EFAULT;
-
-		return 0;
+		return put_user(status, (unsigned int __user *)arg);
 
 	default:
 		return -ENOIOCTLCMD;