phy: phy-mtk-tphy: get optional clock by devm_clk_get_optional()

Use devm_clk_get_optional() to get optional clock

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
1 file changed