M1: compat layer + pf.ko skeleton builds against Linux 7.3.4

- pfk.h: BSD types/ioctl encoding (OpenBSD bit layout), locks (NET_LOCK=rwsem),
  pools, timeouts, mbuf shim over sk_buff, ifnet registry, toeplitz/siphash
- pfk_mod/pfk_hooks: misc /dev/pf (0600), IPv4 netfilter hook skeleton,
  DIOCGETSTATUS answered (M1 skeleton; engine ioctls land with pf_ioctl.c)
- vendorize/stage-port scripts: deterministic upstream staging with seds
  (struct renames, IFF_*->PFIFF_*, sa_len drops) logged to docs/porting-notes
- fixes: modules_prepare+Module.symvers for out-of-tree builds

module/.pf.o.cmd

@@ -0,0 +1,3 @@
+savedcmd_pf.o := ld -m elf_x86_64 --fatal-warnings -z noexecstack --no-warn-rwx-segments   -r -o pf.o @pf.mod  ; /home/lgcosta/lab/linux_kernel/linux-7.3.4/tools/objtool/objtool --hacks=jump_label --hacks=noinstr --hacks=skylake --ibt --prefix=16 --orc --retpoline --rethunk --static-call --uaccess  --link  --module pf.o
+
+pf.o: $(wildcard /home/lgcosta/lab/linux_kernel/linux-7.3.4/tools/objtool/objtool)