Revert "board: rockchip: Fix binman_init failure on EVB-RK3568"

An external TPL binary is now expected to be provided using ROCKCHIP_TPL
when building RK3568 targets.

This reverts commit 31500e7b.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>