UAPI: Guard linux/pmu.h

Place reinclusion guards on linux/pmu.h otherwise the UAPI splitter won't
insert the #include to include the UAPI header from the kernel header.
Signed-off-by: David Howells <dhowells@redhat.com>

include/linux/pmu.h

@@ -6,6 +6,8 @@
  * Copyright (C) 1998 Paul Mackerras.
  */
 
+#ifndef _LINUX_PMU_H
+#define _LINUX_PMU_H
 
 #define PMU_DRIVER_VERSION	2
 
@@ -207,3 +209,5 @@ extern int pmu_sys_suspended;
 #endif
 
 #endif	/* __KERNEL__ */
+
+#endif /* _LINUX_PMU_H */