mmc: mediatek: use data instead of mrq parameter from msdc_{un}prepare_data()

mmc: mediatek: use data instead of mrq parameter from msdc_{un}prepare_data()

[ Upstream commit 151071351bb6f3d1861e99a22c4cebadf81911a0 ]

We already have 'mrq->data' before calling these two functions, no
need to find it again via 'mrq->data' internally. Also remove local
data variable accordingly.

Signed-off-by: Yue Hu <huyue2@yulong.com>
Link: https://lore.kernel.org/r/20210517100900.1620-1-zbestahu@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Stable-dep-of: f5de469990f1 ("mtk-sd: Prevent memory corruption from DMA map failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>