power: supply: max14656: remove set but not used 'ret'

Fix the following gcc warning:

drivers/power/supply/max14656_charger_detector.c:142:6: warning:
variable ‘ret’ set but not used [-Wunused-but-set-variable]
  int ret = 0;
      ^~~

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/max14656_charger_detector.c

@@ -139,9 +139,8 @@ static void max14656_irq_worker(struct work_struct *work)
 
 	u8 buf[REG_TOTAL_NUM];
 	u8 chg_type;
-	int ret = 0;
 
-	ret = max14656_read_block_reg(chip->client, MAX14656_DEVICE_ID,
+	max14656_read_block_reg(chip->client, MAX14656_DEVICE_ID,
 				REG_TOTAL_NUM, buf);
 
 	if ((buf[MAX14656_STATUS_1] & STATUS1_VB_VALID_MASK) &&