mmc: mmci: expand startbiterr to irqmask and error check

All variants don't pretend to have a startbiterr.
-While data error check, if status register return an error
(like  MCI_DATACRCFAIL) we must avoid to check MCI_STARTBITERR
(if not desired).
-expand start_err to MCI_IRQENABLE to avoid to set this bit by default.

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