pf: Add DIOCGETSTATESNV
Add DIOCGETSTATESNV, an nvlist-based alternative to DIOCGETSTATES.
MFC after: 1 week
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D30243
(cherry picked from commit 0592a4c83d67547644763fb023abd5eb28e57f92)