[PATCH v2] Add MCI card support to barebox

[Juergen Beisert]

This is the second series. Hopefully it include all suggestions made.
It also include Sascha's patches related to MCI.

This patch is based on some work Sascha made already. I tried to bring in some
light into the MCI framework routines as they are based on code from another
project. Bear with me, if I didn't add useful comments all over the code. I
just wasn't able to understand what happen... If someone has more knowledge
about MCI cards, please take a look at the FIXME/TODOs and make me understand
why the code does what it does.

There is only one regular user yet: The i.MX27 based PCA100 platform. The other
platform (S3C2440 based) I did the tests on, is not part of barebox (and will not)
and the i.MX23 based platform (ChumbyOne) is not yet part of barebox.

Comments are still welcome.

Regards,
Juergen