Moving ipq-wifi to a dedicated repo

[Ansuel Smith]

As the title said, it was suggested to move the ipq-wifi package
board file to a separate repo.

The problem is that we currently ship many board file with the
openwrt git repo and we always download them.

These won't change that much (or probably forever) and so
shipping them and downloading them by default seems to be
wasted space for other target that don't use it.

I wonder if a better approach would be move these special board
file to a dedicated repo and make the ipq-wifi Makefile to just clone
the repo.

I'm asking for feedback if this would make sense or it not worth it
and would result in added complexity.