Add ICE-V Wireless support

[gojimmypi]

Adds support for new ICE-V Wireless board, based on examples for iCEBreaker.

• Edit: Note this PR requires the related FuseSoC PR https://github.com/fusesoc/fusesoc-cores/pull/15 as well as the SERV fix https://github.com/olofk/serv/pull/90 to work properly as discussed on the Discord channel . Without the POR delay, the select LED would illuminate, but not blink. This PR works for the Zephyr Hello World hex:

# from your fusesoc project directory:
fusesoc run --target=icev_wireless servant --memfile=fusesoc_libraries/serv/sw/zephyr_hello.hex
python3 ../ICE-V-Wireless/python/send_c3sock.py -a 192.168.1.28 --flash ./build/servant_1.1.0/icev_wireless-icestorm/servant_1.1.0.bin

I was not able to get the default hello to work. As there is no Zephyr source code available to compare, I am not sure exactly what the problem might be. See notes on Discord.

See also the related https://github.com/fusesoc/blinky/pull/89

I have further details of my ICE-V Wireless SERV and FuseSoc experience on my blog: https://gojimmypi.github.io/ICE-V-Wireless-SERV-fusesoc/

[olofk]

This one completely slipped my mind. Finally got around to merge it now, but I left out the .gitignore changes with the motivation that it's not intended to work from inside the repo. Thank you for your contributions!