mmc: arm_pl180_mmci: Rely on DM

mmc: arm_pl180_mmci: Rely on DM

The PL180/MMCI driver is implied to use CONFIG_DM and the ARM
defconfigs such as configs/vexpress_ca9x4_defconfig will get it
as well.

With a simple oneline to default to not being the v2 variant,
the original ARM MMCI variant works fine with the driver as well.
The IP version actually needs to be read out from a register on
the ARM versions, but we will simply assume we are running on the
original hardware if arm,primecell-periphid is not explicitly
specified in the device tree.

Drop the !CONFIG_DM code and depend on DM_MMC.

Tested on the Versatile Express CA9x4 board.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>