mmc: Driver for CB710/720 memory card reader (MMC part)

The code is divided in two parts. There is a virtual 'bus' driver
that handles PCI device and registers three new devices one per card
reader type. The other driver handles SD/MMC part of the reader.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Pierre Ossman <pierre@ossman.eu>