rtc: hym8563: fix a missing check of block data read

When i2c_smbus_read_i2c_block_data() fails, the read data in "buf" could
be incorrect and should not be used. The fix checks if
i2c_smbus_read_i2c_block_data fails, and if so, return its error code
upstream.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-hym8563.c

@@ -109,6 +109,8 @@ static int hym8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	}
 
 	ret = i2c_smbus_read_i2c_block_data(client, HYM8563_SEC, 7, buf);
+	if (ret < 0)
+		return ret;
 
 	tm->tm_sec = bcd2bin(buf[0] & HYM8563_SEC_MASK);
 	tm->tm_min = bcd2bin(buf[1] & HYM8563_MIN_MASK);