Eliminate SIOCGIFADDR handling in bpf.

Quoting 19 years bpf.4 manual from bpf-1.2a1:
"
(SIOCGIFADDR is obsolete under BSD systems. SIOCGIFCONF should be
used to query link-level addresses.)
"

• SIOCGIFADDR was not imported in NetBSD (bpf.c 1.36) and OpenBSD.
• Last bits (e.g. manpage claiming SIOCGIFADDR exists) was cleaned from NetBSD via kern/21513 5 years ago, from OpenBSD via documentation/6352 5 years ago.