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

sys/compat/linuxkpi/common/include/linux/hardirq.h

@@ -31,6 +31,7 @@
 
 #include <linux/types.h>
 #include <linux/lockdep.h>
+#include <linux/preempt.h>
 
 #include <sys/param.h>
 #include <sys/bus.h>

sys/compat/linuxkpi/common/include/linux/highmem.h

@@ -45,6 +45,7 @@
 
 #include <linux/mm.h>
 #include <linux/page.h>
+#include <linux/hardirq.h>
 
 #define	PageHighMem(p)		(0)
 

sys/compat/linuxkpi/common/include/linux/spinlock.h

@@ -41,6 +41,7 @@
 #include <linux/rwlock.h>
 #include <linux/bottom_half.h>
 #include <linux/lockdep.h>
+#include <linux/preempt.h>
 
 typedef struct mtx spinlock_t;