MODULE_PNP_INFO(9): Add example of T usage.

Provide an example of specifying a common vendor value as the documentation
is not clear enough at the moment.

While here, add 'D:#' to the previous example to eat the remaining
description string.

Also, pet mandoc a bit.

Submitted by: Yuri Pankov <yuripv@yuripv.net>
Reviewed by: cem, imp
Approved by: re (kib), krion (mentor, implicit), mat (mentor, implicit)
Differential Revision: https://reviews.freebsd.org/D17321