u-boot: Detect CPU revision

[openedev]

Reference:

https://github.com/radxa/kernel/blob/linux-5.10-gen-rkr4.1/drivers/cpufreq/rockchip-cpufreq.c#L231

1. Find the CPU version
2. Print the found CPU

sample log

CPU:   Rockchip RK3588J rev1.2 at 792MHz
CPU:   Industrial temperature grade (-40C to +85C) at 28C

3. Enable SPL multi DTB for Neu6a, Neu6b
4. Load the right dtb based on the found CPU
5. Support this in Mainline as well BSP U-boot.

[openedev]

SoM 6:  NCM6B or Neu6b: RK3588J
Som 12: NCM6A or Neu6A: RK3588

[openedev]

git clone https://github.com/rockchip-linux/rkbin.git
git clone https://github.com/openaia/u-boot && cd u-boot
export BL31=../rkbin/bin/rk35/rk3588_bl31_v1.40.elf
export ROCKCHIP_TPL=../rkbin/bin/rk35/rk3588_ddr_lp4_2112MHz_lp5_2736MHz_v1.12.bin
make neu6b-io-rk3588_defconfig
make -j 16
sudo dd if=u-boot-rockchip.bin of=/dev/sdX seek=64 && sudo sync