mmc: mmci: add variant properties to define cpsm & cmdresp bits

This patch adds command variant properties to define
cpsm enable bit and responses.
Needed to support the STM32 variant (shift of cpsm bit,
specific definition of commands response).

Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>