nrf52840-mdk-usb-dongle.conf: Add new machine from makerdiary

It was tested with zephyr-openthread-rcp along Oniro's IoT gateway blueprint

For the record deployment was done manually:

• Click on device button
• uf2conv.py "zephyr.hex" -c -f 0xADA52840
• and then copy to mounted "/dev/disk/by-label/MDK-DONGLE"

Support of unfree flashing tools might be added later (once double verified)

Forwarded: https://lists.yoctoproject.org/g/yocto/message/58142 Relate-to: eclipse/oniro-blueprints/transparent-gateway/meta-oniro-blueprints-gateway#6 Relate-to: https://wiki.makerdiary.com/nrf52840-mdk/zephyr/ Relate-to: https://gitlab.eclipse.org/pcoval/oniro-presentations/-/wikis/openthread Signed-off-by: Philippe Coval philippe.coval@astrolabe.coop