mc13xxx: add I2C support

[Marc Reilly]

Hi,

This series (based on 3.2) adds I2C support for the mc13xxx family PMICs.
The patches are similar, but not identical to my previous patches for this [1], the
main difference being the way the config items are done in patch 2.

I don't have the hardware to retest on SPI hardware, I'd appreciate if someone could 
double check it still works.

I've also got a stack of patches for the mc13xxx to follow, but should get this in
first.

Cheers,
Marc

[1]
http://lists.infradead.org/pipermail/linux-arm-kernel/2011-January/thread.html#36936