mmci: Add support for ST Micro derivate

This patch adds support for the ST Microelectronics version of
the PL180 PrimeCell. They use designer ID 0x80 and have a few
alterations/bugfixes related to open drain and HW flow control.
They also add some SDIO registers, I am unsure if these are
in ST HW only or if this is things also added in later ARM
revisions, but they are included in the mmci.h file for
completeness.

Signed-off-by: Linus Walleij <linus.walleij@ericsson.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>