rockchip: rk3128: remove noop file

arch_cpu_init is already returning 0 in its weak definition in
common/board_f.c so let's just remove the file entirely since nothing
else is done in it.

Cc: Quentin Schulz <foss+uboot@0leil.net>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>