phy: mediatek: statify mtk_hdmi_phy_driver

mtk_hdmi_phy_driver is not declared as static, so statify it.

drivers/phy/mediatek/phy-mtk-hdmi.c:204:24: warning: symbol 'mtk_hdmi_phy_driver' was not declared. Should it be static?
Acked-by: NChun-Kuang Hu <chunkuang.hu@kernel.org>
Link: https://lore.kernel.org/r/20201205091146.3184305-1-vkoul@kernel.orgSigned-off-by: NVinod Koul <vkoul@kernel.org>

drivers/phy/mediatek/phy-mtk-hdmi.c

@@ -201,7 +201,7 @@ static const struct of_device_id mtk_hdmi_phy_match[] = {
 	{},
 };
 
-struct platform_driver mtk_hdmi_phy_driver = {
+static struct platform_driver mtk_hdmi_phy_driver = {
 	.probe = mtk_hdmi_phy_probe,
 	.driver = {
 		.name = "mediatek-hdmi-phy",