LinuxKPI: add supporting #includes

Compiling drm-kmod on !X86 does not include asm/smp.h which includes
preempt.h on FreeBSD. In order to compile drm-kmod on other
architectures add the secondary #includes for preempt.h to
spinlock.h and hardirq.h (which now also gets included from highmem.h)
to connect the #include chain.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
PR: 279864
Reviewed by: jhibbits, emaste
Differential Revision: https://reviews.freebsd.org/D55974