configs: rk3328: enable TPL for rock64-rk3328_defconfig

Until now, binary TPL by Rockchip has been required for booting
procedure. Starting from this commit we may use only u-boot to boot
the device.

Note, that using binary TPL instead of U-boot TPL is still working.

Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>