wiki page udpates

[Greg Troxel <gdt%lexort.com@localhost>]

I have updated the wiki a bit, as penance for asking people to explain
things to me.

In particular, at:

  https://wiki.netbsd.org/ports/evbarm/raspberry_pi/

I assumed/declared that anyone running 7 is up to date (and thus
merged/dropped a lot of "before mid 2017" vs "after the backport"
stuff).  I also did some rototill/cleanup/tightening.  I'm not trying to
be too heavyhanded, and guessing that it's just that no one else has
gotten around to it.  But if you object, please speak up.

One thing I don't understand is firmware updates.  The section at the
end was (I think!) about developers updating the firmware in the NetBSD
source tree.  It seems obvious that this firmware should be in the
installed system image someplace, and that updating it on a particular
system is kind of like updating bootxx_ffsv1 and /boot (to use i386
examples).  But I don't find it, and I wonder if it's used to build the
image, and not installed, and how people are supposed to update.

Another question is the Pi 0 and Pi 0 W.   I gather these work fine,
except the builtin wifi/bluetooth on the 0W is the same situation as the
3.  Is that right?

I would like to purge a bunch of the comments.  Many of them were very
useful when made -- long ago -- and are often requests for
clarification.  So I view them as tickets and would like to delete them
if that the document has been improved to answer the questions they ask.
Please speak up on the list if you object to this sort of cleanup (and
if so, what you think we should do instead).