ARM: ux500: Fork cpu-db8500 platform_devs for sequential DT enablement

To aid in sequential one-by-one Device Tree enablement, we split
cpu-db8500's platform_devs structure into normal platform boot, where
we leave all devices to be added in tact and a DT version where we
will remove the devices as they are DT enabled.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>