rockchip: rk3328: add rock64-rk3328_defconfig

rockchip: rk3328: add rock64-rk3328_defconfig

The ROCK64 is a credit card size SBC based on Rockchip RK3328
Quad-Core ARM Cortex A53.

This series allow building u-boot SPL and u-boot.itb for Rock64
board. The proprietary TPL is stil required for deploy:

  ./tools/mkimage -n rk3328 -T rksd \
    -d ./rkbin/bin/rk33/rk3328_ddr_333MHz_v1.16.bin idbloader.img
  cat ./spl/u-boot-spl.bin >> idbloader.img
  dd if=idbloader.img of=/dev/sdcard seek=64 conv=notrunc
  dd if=u-boot.itb of=/dev/sdcard seek=16384 conv=notrunc

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