pf: rename the pf_pdesc field rh_cnt to badopts

It is also used for IPv4 options now.
ok mcbride@ henning@

Reviewed by: zlei
Obtained from: OpenBSD, bluhm <bluhm@openbsd.org>, 4fe6abd45f
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D46650