net: mdio: xgene: Fix unused xgene_mdio_of_match warning for !CONFIG_OF

Commit a243ecc3 ("net: mdio: xgene: Use device_get_match_data()")
dropped the unconditional use of xgene_mdio_of_match resulting in this
warning:

drivers/net/mdio/mdio-xgene.c:303:34: warning: unused variable 'xgene_mdio_of_match' [-Wunused-const-variable]

The fix is to drop of_match_ptr() which is not necessary because DT is
always used for this driver (well, it could in theory support ACPI only,
but CONFIG_OF is always enabled for arm64).

Fixes: a243ecc3 ("net: mdio: xgene: Use device_get_match_data()")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202310170832.xnVXw1bb-lkp@intel.com/Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20231019182345.833136-1-robh@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/mdio/mdio-xgene.c

@@ -437,7 +437,7 @@ static void xgene_mdio_remove(struct platform_device *pdev)
 static struct platform_driver xgene_mdio_driver = {
 	.driver = {
 		.name = "xgene-mdio",
-		.of_match_table = of_match_ptr(xgene_mdio_of_match),
+		.of_match_table = xgene_mdio_of_match,
 		.acpi_match_table = ACPI_PTR(xgene_mdio_acpi_match),
 	},
 	.probe = xgene_mdio_probe,