sys: Bump non-ISA PNP removal to 16.0

This may include atkbdc, which is not being removed in 15.0.

Approved by: re (cperciva)
Sponsored by: The FreeBSD Foundation

(cherry picked from commit 46f982122c0d670ac181b748a5b8c2b221f61517)
(cherry picked from commit db84583a939f3d678a0c3f5e2ec599c7f9964118)