LinuxKPI: lockdep fix #includes

Add sys/sytm.h for __diagused which unbreaks compilation of
drm-kmod 5.10-lts on main.

Sponsored by: The FreeBSD Foundation
Reported by: Evgenii Khramtsov
PR: 282479
Fixes: 5c92f84bb607

(cherry picked from commit 9b2705121ba230bf71a1509cc928f0481dfbf31c)