iwn.4: move hardware to HARDWARE + minor cleanup

[concussious.bugzilla_runbox.com]

Summary

iwn.4: move hardware to HARDWARE + minor cleanup

Add devices supported by this driver to a HARDWARE section
for inclusion in the release Hardware Compatibility Notes.
While here:

+ add networking(7) quick start guide
+ tweak examples for consistency
+ tag spdx

MFC after:      3 days

If this is acceptable, please git commit --author ="Alexander Ziaee <[e-mail]>". Thanks!

Test Plan

Read rendered manual page