qlogic: check kstrtoul() for errors

We accidentally left out the error handling for kstrtoul().

Fixes: a520030e326a ("qlcnic: Implement flash sysfs callback for 83xx adapter")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qlcnic/qlcnic_sysfs.c

@@ -1128,6 +1128,8 @@ static ssize_t qlcnic_83xx_sysfs_flash_write_handler(struct file *filp,
 	struct qlcnic_adapter *adapter = dev_get_drvdata(dev);
 
 	ret = kstrtoul(buf, 16, &data);
+	if (ret)
+		return ret;
 
 	switch (data) {
 	case QLC_83XX_FLASH_SECTOR_ERASE_CMD: