perf tools: Protect header files with a consistent style

There was a colorful mix of header guards - standardize them.

Signed-off-by: John Kacur <jkacur@redhat.com>
LKML-Reference: <alpine.LFD.2.00.0909241756530.11383@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 6e84907..ee164f6 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -1,5 +1,5 @@
-#ifndef _PERF_SYMBOL_
-#define _PERF_SYMBOL_ 1
+#ifndef __PERF_SYMBOL
+#define __PERF_SYMBOL 1
 
 #include <linux/types.h>
 #include "types.h"
@@ -89,4 +89,4 @@
 extern struct dso *hypervisor_dso;
 extern const char *vmlinux_name;
 extern int   modules;
-#endif /* _PERF_SYMBOL_ */
+#endif /* __PERF_SYMBOL */