mmc: mediatek: make hs400_tune_response only for mt8173

the origin design of hs400_tune_response is for mt8173 because of
mt8173 has a special design. for doing that, we add a new member
"compatible", by now it's only for mt8173.

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>