mmc: mtk-sd: Remove unused parameters(mrq)

The mmc_request structure(*mrq) is not used. //msdc_cmd_find_resp
I remove the unnecessary code related to the mmc_request structure.

Signed-off-by: ChanWoo Lee <cw9316.lee@samsung.com>
Link: https://lore.kernel.org/r/20210827093119.32481-1-cw9316.lee@samsung.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>