sysinfo.h: Add re-inclusion guard

Add #ifndef __SYSINFO_H__ ... #endif to prevent re-inclusion of this
file.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/sysinfo.h b/include/sysinfo.h
index 68fad25..8054d4d 100644
--- a/include/sysinfo.h
+++ b/include/sysinfo.h
@@ -4,6 +4,9 @@
  * Mario Six,  Guntermann & Drunck GmbH, mario.six@gdsys.cc
  */
 
+#ifndef __SYSINFO_H__
+#define __SYSINFO_H__
+
 struct udevice;
 
 /*
@@ -228,3 +231,4 @@
 }
 
 #endif
+#endif