mmc: arm_pl180_mmci: Update to support CONFIG_BLK

Config flag CONFIG_BLK becomes mandatory, update arm_pl180_mmci
to support this config.

This driver is used by STM32Fx and by Vexpress platforms.
Only STM32Fx are DM ready. No DM code is isolated and will be
removed easily when wexpress will be converted to DM.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>