phy: phy-mtk-mipi-dsi: remove dummy assignment of error number

Return the error number directly without assignment

Acked-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1629191987-20774-8-git-send-email-chunfeng.yun@mediatek.com


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