Add support for keyboard used in Samsung Chromebook (ARM machine)

Support covers device drivers for:
- Interrupt Combiner
- gpio/pad, External Interrupts Controller (pad)
- I2C Interface
- Chrome Embedded Controller
- Chrome Keyboard

Also:
- Use new gpio dev class in EHCI driver
- Expand device tree information
Give hint on how to disable the default repository.

Discussed with:	bapt
MFC after:	instantly (preparing EN)