turris-mox-firmware: update devel version to v3 of reboot issue workaround
This PR updates secure-firmware-devel.bin and adds uboot-devel file for uboot update.
Uses files from https://gitlab.nic.cz/turris/mox-boot-builder/-/releases/v2021.04.09
sha256 for firmware files:
- b423a8580ca62adf5b6ae7d10caa2c4b10aaaa7101acd58cf7b874cdacb6f541 secure-firmware-devel.bin
Edited by Jan Pavlinec