U-Boot loader and related files for the radxa zero3e, zero3w

To install this bootloader on an sdcard just do:

dd if=/usr/local/share/u-boot/u-boot-radxa-zero3/idbloader.img of=/path/to/sdcarddevice seek=64 conv=sync
dd if=/usr/local/share/u-boot/u-boot-radxa-zero3/u-boot.itb of=/path/to/sdcarddevice seek=16384 bs=512 conv=sync