Bring initial support for Allwinner A20 SoC (Cubieboard2).
Add support for A20 timer.
Correct interrupt offset depending from chip.
Add basic code for CPU configuration module.
For now, add kernel config and dts file
(only FDT blob related problem needs to be solved later in
order to have one kernel for both cubieboard1 and 2).

Approved by: ray@