mmc: core: drop unnecessary bit checking

This if-block is going to call mmc_card_set_blockaddr(), so
mmc_card_blockaddr() right before it is redundant.

I am fixing the block comment style while I am here.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>