Adjust function definitions in pf.c to avoid clang 15 warnings
With clang 15, the following -Werror warnings are produced:
sys/netpfil/pf/pf.c:985:19: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] pf_mtag_initialize() ^ void sys/netpfil/pf/pf.c:995:14: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] pf_initialize() ^ void sys/netpfil/pf/pf.c:1089:16: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] pf_mtag_cleanup() ^ void sys/netpfil/pf/pf.c:1096:11: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] pf_cleanup() ^ void sys/netpfil/pf/pf.c:1989:27: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] pf_purge_expired_src_nodes() ^ void sys/netpfil/pf/pf.c:2174:24: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes] pf_purge_unlinked_rules() ^ void
This is because pf_mtag_initialize(), pf_initialize(),
pf_mtag_cleanup(), pf_cleanup(), pf_purge_expired_src_nodes(), and
pf_purge_unlinked_rules() are declared with (void) argument lists, but
defined with empty argument lists. Make the definitions match the
declarations.
MFC after: 3 days
(cherry picked from commit 503b5870c018ec342be1396896560b720945d7e5)