rockchip: rk3188: enable remap function

Most Rockchip socs have the ability to either map the bootrom or a sram
area to the starting address of the cpu by flipping a bit in the GRF.

Newer socs leave this untouched and mapped to the bootrom but the legacy
loaders on rk3188 and before enabled the remap functionality and the
current smp implementation in the Linux kernel also requires it to be
enabled, to bring up secondary cpus.

So to keep smp working in the kernel, mimic the behaviour of the legacy
bootloaders and enable the remap functionality.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Simon Glass <sjg@chromium.org>