rockchip: arm: use 'arch-rockchip' for common header
rockchip platform header file is in 'arch-rockchip'
instead of arch-$(SOC) for all SoCs.
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>