phy: mediatek: ufs: use common register access helpers

No need define private register access helpers, use common ones defined
in phy-mtk-io.h

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220920090038.15133-5-chunfeng.yun@mediatek.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>