rockchip: Add params_setup to RK3328.

params_setup.c provides the function params_early_setup, which
takes care of parsing ATF parameters (bl31_plat_param array,
fdt or coreboot table). As params_early_setup is defined as weak
symbol in bl31_plat_setup.c, providing a platform-specific
bl31_plat_setup implementation is optional.

This patch adds the rockchip-common params_setup.c to the sources
for RK3328. This streamlines the parameter handling for all supported
rockchip SoCs.

Signed-off-by: Christoph Müllner <christophm30@gmail.com>
Change-Id: I071c03106114364ad2fc408e49cc791fe5b35925