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
Approved by: re (cperciva)

(cherry picked from commit 9b2705121ba230bf71a1509cc928f0481dfbf31c)
(cherry picked from commit 06733ceca677b2d8ea2ae738bbb624d510fc9df8)