sanitize linux/isdn_divertif.h for userspace

the isdn_divertif contains kernel-only references so I've wrapped them in
__KERNEL__ and add proper #include statements.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Karsten Keil <kkeil@suse.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>