Fix previous commit: unbreak build of libkvm by including sys/systm.h

only when _KERNEL is defined.

Approved by:	re@ (implicit)

sys/ia64/include/pcpu.h

@@ -31,7 +31,6 @@
 #define	_MACHINE_PCPU_H_
 
 #include <sys/sysctl.h>
-#include <sys/systm.h>
 #include <machine/pcb.h>
 
 struct pcpu_stats {
@@ -72,6 +71,8 @@ struct pcpu_md {
 
 #ifdef _KERNEL
 
+#include <sys/systm.h>
+
 struct pcpu;
 
 register struct pcpu * volatile pcpup __asm__("r13");