Some MMC drivers describe operations with the DM_MMC_OPS form, but
there are still several drivers with older implementation.  We can
not compile drivers from different groups at the same time because
the core framework is shared with #ifdef CONFIG_DM_MMC_OPS.

Every driver should have "depends on DM_MMC_OPS" (or !DM_MMC_OPS)
explicitly to express which framework it is based on.  This will
avoid enabling drivers with incompatible interface at the same time.
It is incorrect to make a driver "select DM_MMC_OPS".

While we are here, add "depends on OF_CONTROL" as well because this
driver can be configured only by Device Tree.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>