ARM: nomadik: initial devicetree support

Support basic device tree boot on the Nomadik. Implement the
support in the cpu file with the intent of deleting the board
files later. At this stage IRQ controllers, system timer,
l2x0 cache, UARTs and thus console boot is fully functional.
Patch out the code adding devices by initcalls for now so
as not to disturb the boot.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>