LinuxKPI: Add linux/dynamic_debug.h header

Sponsored by: Serenity Cyber Security, LLC
Obtained from: OpenBSD
Reviewed by: manu
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D42815

(cherry picked from commit 2b037743a77dcf31095fe1fedd21870b3aa6494b)