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.ko.cmd

@@ -0,0 +1 @@
+savedcmd_pf.ko := ld -r -m elf_x86_64 --fatal-warnings -z noexecstack --no-warn-rwx-segments --build-id=sha1 --force-group-allocation  -T /home/lgcosta/lab/linux_kernel/linux-7.3.4/scripts/module.lds -o pf.ko pf.o pf.mod.o .module-common.o