rockchip: Convert all boards to use binman

rockchip: Convert all boards to use binman

Instead of the bash script, use binman to generate the FIT for arm64.

For 32-bit boards, use binman for all images, dropping the intermediate
files.

With this change, only Zynq is now using SPL_FIT_GENERATOR so update the
Kconfig rule accordingly.

Clean up the Makefile to the extent possible. Unfortunately, two boards
do not use SPL_FRAMEWORK so don't enable the u-boot.img rule:

   evb-rk3036
   kylin-rk3036

So a small remnant remains.

Signed-off-by: Simon Glass <sjg@chromium.org>