Turns out, echoing it into the cmdline.txt file was causing it to be
added as a second line, which means it gets dropped, so use sed to add
it to the end of the line.
This service is so buggy, and has been reported for years in the debian
bugtracker as not working properly, so to keep from it possibly failing,
just remove it from starting in the first place.
The P4wnp1 needs the groups added before the system boots for the first
time, because the udev rules happen earlier, so add them in here instead
of in the bsp
Because we use --depth 1 when cloning the firmware repository, we can't
actually do a checkout. Luckily, they tag the releases, so we use the
tag for the same date that has the release we want.
