rockchip: Use an external TPL binary on RK3588

There is no support to initialize DRAM on RK3588 SoCs using U-Boot TPL
and instead an external TPL binary must be used to generate a bootable
u-boot-rockchip.bin image.

Enable ROCKCHIP_EXTERNAL_TPL by default for RK3588, add build steps for
RK3588 to documentation and clean up CONFIG_BINMAN_FDT options.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Jagan Teki <jagan@edgeble.ai>
4 files changed