man4: wifi manuals: revise .Sh HARDWARE + polish some

The Release Hardware Notes are generated from hardware sections in the
manual pages. Create or organize these sections in Wi-Fi driver manuals
for information flow, and perform minor maintenance on them while here.

After some testing, we have determined that a compact column list is
the best for a single column listing in the hardware release notes.
This makes very clean subsections and is for some reason denser than
using a tagged list.

This adds the long requested conversion from netmask to cidr examples.
These examples probably shouldn't even be here, but that is a discussion
for another day.

X-MFC with: 8f1a2d507e25e77d20a5
Reported by: bz (relnotes generation, cidr, test-net-1 ip4addr)
Reported by: grahamperrin (HARDWARE order mentioned in fdp-primer)
Reported by: Graham Percival <gperciva@tarsnap.com> (don't prompt)
Reviewed by: bz (anything wrong likely is my polishing fault; incl. iwm.4)
Differential Revision: https://reviews.freebsd.org/D47508

(cherry picked from commit 8f1a2d507e25e77d20a5d7675dc8eee9b83d3570)
(cherry picked from commit 93b30f1b6caec5083efacf3fb5049b72e75cc09e)