mmc: arm_pl180_mmci: adapt driver to DM usage

Convert this driver to driver model.
This driver is also used by VEXPRESS platforms which doesn't
use driver model.

Tested on STM32F746 and STM32F769 platforms.

Signed-off-by: Christophe Priouzeau <christophe.priouzeau@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>