Test of OpenThread RCP on Nordic hardware

[Nerivec]

Early experimentation from puddly points to transmission issues (reception appears fine) when using STREAM_RAW mode with Nordic firmware/hardware.
Anyone willing and able to build and experiment some more, please share your findings here!

Example from OpenThread: https://github.com/openthread/ot-nrf528xx

CC: @kirovilya @puddly @antst

[kirovilya]

Can not build fw for my NRF52840 (Nice! Nano v2.0) :(