net: txgbe: Fix unsigned comparison to zero in txgbe_calc_eeprom_checksum()

The error checks on checksum for a negative error return always fails because
it is unsigned and can never be negative.

Fixes: 049fe536 ("net: txgbe: Add operations to interact with firmware")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/wangxun/txgbe/txgbe_hw.c

@@ -200,10 +200,11 @@ static int txgbe_calc_eeprom_checksum(struct txgbe_hw *hw, u16 *checksum)
 	if (eeprom_ptrs)
 		kvfree(eeprom_ptrs);
 
-	*checksum = TXGBE_EEPROM_SUM - *checksum;
-	if (*checksum < 0)
+	if (*checksum > TXGBE_EEPROM_SUM)
 		return -EINVAL;
 
+	*checksum = TXGBE_EEPROM_SUM - *checksum;
+
 	return 0;
 }