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