drivers: net: xgene: Make xgene_enet_of_match depend on CONFIG_OF

If CONFIG_NET_XGENE=y but CONFIG_OF=n:

drivers/net/ethernet/apm/xgene/xgene_enet_main.c:1033: warning: ‘xgene_enet_of_match’ defined but not used
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -1030,12 +1030,14 @@ static const struct acpi_device_id xgene_enet_acpi_match[] = {
 MODULE_DEVICE_TABLE(acpi, xgene_enet_acpi_match);
 #endif
 
+#ifdef CONFIG_OF
 static struct of_device_id xgene_enet_of_match[] = {
 	{.compatible = "apm,xgene-enet",},
 	{},
 };
 
 MODULE_DEVICE_TABLE(of, xgene_enet_of_match);
+#endif
 
 static struct platform_driver xgene_enet_driver = {
 	.driver = {