pflog/pfsync: Fix module build with VIMAGE=yes

pflog and pfsync's module Makefile fails to include opt_global.h to SRCS
leading to build error for VIMAGE case.

Reproduced with:
cd /usr/src/sys/modules/pflog && make VIMAGE=yes

PR: 229404
Submitted by: eugen@
MFC after: 1 week