mmc: mmci: stm32: correctly check all elements of sg list

Use sg and not data->sg when checking sg list elements. Else only the
first element alignment is checked.
The last element should be checked the same way, for_each_sg already set
sg to sg_next(sg).

Fixes: 46b723dd

 ("mmc: mmci: add stm32 sdmmc variant")
Cc: stable@vger.kernel.org
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Link: https://lore.kernel.org/r/20220317111944.116148-2-yann.gautier@foss.st.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>