mmc: mediatek: tune CMD/DATA together

for MSDC IP which supports both data tune and async fifo, it can
tune cmd/data together. which can save the time and make the tune
result of CMD more stable as data line are 4bit or 8bit.

Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>