phy: mediatek: Add UFS M-PHY driver

Add UFS M-PHY driver on MediaTek chipsets.

Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>