net/xgene: fix Wvoid-pointer-to-enum-cast warning

'enet_id' is an enum, thus cast of pointer on 64-bit compile test with
W=1 causes:

  xgene_enet_main.c:2044:20: error: cast to smaller integer type 'enum xgene_enet_id' from 'const void *' [-Werror,-Wvoid-pointer-to-enum-cast]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Simon Horman <horms@kernel.org> # build-tested
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/apm/xgene/xgene_enet_main.c

@@ -2041,7 +2041,7 @@ static int xgene_enet_probe(struct platform_device *pdev)
 
 	of_id = of_match_device(xgene_enet_of_match, &pdev->dev);
 	if (of_id) {
-		pdata->enet_id = (enum xgene_enet_id)of_id->data;
+		pdata->enet_id = (uintptr_t)of_id->data;
 	}
 #ifdef CONFIG_ACPI
 	else {