rtc: abx80x: return meaningful value for RTC_VL_READ

ABX8XX_STATUS_BLF indicates the battery is low and needs to be replaced
soon.

Link: https://lore.kernel.org/r/20191214220259.621996-4-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-abx80x.c

@@ -523,12 +523,9 @@ static int abx80x_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 		if (status < 0)
 			return status;
 
-		tmp = !!(status & ABX8XX_STATUS_BLF);
+		tmp = status & ABX8XX_STATUS_BLF ? RTC_VL_BACKUP_LOW : 0;
 
-		if (copy_to_user((void __user *)arg, &tmp, sizeof(int)))
-			return -EFAULT;
-
-		return 0;
+		return put_user(tmp, (unsigned int __user *)arg);
 
 	case RTC_VL_CLR:
 		status = i2c_smbus_read_byte_data(client, ABX8XX_REG_STATUS);