ARM: integrator: hook the CP into the SoC bus

This hooks the Integrator/CP into the SoC bus when booting from
device tree, by mapping the CP controller registers first,
then registering the SoC device, and then populating the device
tree with the SoC device as parent.

Cc: Lee Jones <lee.jones@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>