mmc: mediatek: add HS400 enhanced strobe support

Add support for HS400ES mode to MediaTek MMC Card Driver.

Signed-off-by: Wenbin Mei <wenbin.mei@mediatek.com>
Link: https://lore.kernel.org/r/20201102092822.5301-2-wenbin.mei@mediatek.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>