wpi.4: move hardware to HARDWARE + minor cleanup

Add devices supported by this driver to a HARDWARE section
for generation in the Hardware Compatibility Notes.

While here:

• describe more consistently with product doc and rest of manual
• consolidate basics in first paragraph of description
• mention boot time configuration
• cross-ref networking(7) quick start guide
• zap deprecated Tn, macro in list width, and "Dq Li" => "Ql"
• markup some unmarked elements
• add SPDX tag

MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D47170