2023-02-19 release

U-Boot port for BL808, 2023-02-19 release

Based on upstream v2023.04-rc2.

M0 variant:
 - defconfig: ox64_m0_defconfig
 - UART: GPIO14/15 at 115200 baud (matches M1s dock)
 - build instructions:
 	make CROSS_COMPILE=riscv32-linux-musl- ox64_m0_defconfig
	make CROSS_COMPILE=riscv32-linux-musl-
	bflb-mcu-tool --chipname bl808 --port /dev/ttyUSB1 \
		--baudrate 2000000 --firmware u-boot.bin

D0 variant:
 - defconfig: ox64_d0_defconfig
 - UART: GPIO16/17 at 115200 baud (matches M1s dock)
 - works with latest upstream OpenSBI or
   https://github.com/openbouffalo/opensbi/commits/bl808
 - build instructions:
 	make CROSS_COMPILE=riscv64-linux-musl- ox64_d0_defconfig
	make CROSS_COMPILE=riscv64-linux-musl-
	cd ../opensbi
	make CROSS_COMPILE=riscv64-linux-musl- PLATFORM=generic \
		FW_FDT_PATH=../u-boot/arch/riscv/dts/bl808-d0-ox64.dtb \
		FW_PAYLOAD_FDT_ADDR=0x50080000 \
		FW_PAYLOAD_OFFSET=0x100000 \
		FW_PAYLOAD_PATH=../u-boot/u-boot.bin \
		FW_TEXT_START=0x50000000
	strip --strip-all build/platform/generic/firmware/fw_payload.elf

Booting D0 from M0:
	# Load fw_payload.elf from MMC
	load mmc 0:1 51000000 fw_payload.elf
	# Or load it over Ethernet (this may require multiple attempts)
	dhcp
	tftpboot 51000000 fw_payload.elf
	# Unpack the ELF and start up D0.
	# You can repeat the last command to reload/reset D0.
	rproc init 0
	rproc stop 0; rproc load 0 51000000 100000; rproc start 0