mmc: mediatek: add async fifo and data tune support

mt2701/mt2712 supports async fifo & data tune, which can improve
host stability.

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