net: sparx5: Fix reading of the MAC address

There is an issue with the checking of the return value of
'of_get_mac_address', which returns 0 on success and negative value on
failure. The driver interpretated the result the opposite way. Therefore
if there was a MAC address defined in the DT, then the driver was
generating a random MAC address otherwise it would use address 0.
Fix this by checking correctly the return value of 'of_get_mac_address'

Fixes: b74ef9f9 ("net: sparx5: Do not use mac_addr uninitialized in mchp_sparx5_probe()")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/sparx5/sparx5_main.c

@@ -834,7 +834,7 @@ static int mchp_sparx5_probe(struct platform_device *pdev)
 	if (err)
 		goto cleanup_config;
 
-	if (!of_get_mac_address(np, sparx5->base_mac)) {
+	if (of_get_mac_address(np, sparx5->base_mac)) {
 		dev_info(sparx5->dev, "MAC addr was not set, use random MAC\n");
 		eth_random_addr(sparx5->base_mac);
 		sparx5->base_mac[5] = 0;