Remove $FreeBSD$: two-line nroff pattern

Remove /^\.\\"\n\.\\"\s*\$FreeBSD\$$\n/

Add warning that the PNP info has to follow the module declaration.

Due to how the linker.hints file is laid out, we'll associate the pnp
info with the wrong module if the module declaration comes after the
pnp info. Until that limiation is removed, we need to have this
ordering. Ideally, we'd also enforce the ordering somehow, but I've
come up with no way to do that yet...

MODULE_PNP_INFO(9): catch up with r338948, and remove the element size
parameter from the man page.

Reviewed by: cem, imp
Approved by: re (gjb), kib (mentor)
Differential Revision: https://reviews.freebsd.org/D17436

MODULE_PNP_INFO(9): Fix a grammar mistake.

Reported by: ak
Reviewed by: imp, Yuri Pankov <yuripv@yuripv.net>
Approved by: re (gjb), krion (mentor, implicit), mat (mentor, implicit)
Differential Revision: https://reviews.freebsd.org/D17403

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

Note that MODULE_PNP_INFO has to come after a DRIVER_MODULE.

Add description for T specifier. It's for PNP keys that are checked
programatically that must be true for a device to match, but aren't in
the table as discrete fields.

Sponsored by: Netflix

Take a first stab at documenting use of MODULE_PNP_INFO

Sponsored by: Dell EMC Isilon