nda.4: Add a HARDWARE section, tag SPDX

The description likely also needs some love.

MFC after: 1 hour
Co-authored-by: ziaee (typed up imps suggestion, tagged spdx)
Differential Revision: https://reviews.freebsd.org/D52866

(cherry picked from commit f19aea89abd8964bf96d134c2bd6e127464c79f6)