AP_EPM: replace header guard with pragma once

libraries/AP_EPM/AP_EPM.h

@@ -11,9 +11,7 @@
 
 /// @file	AP_EPM.h
 /// @brief	AP_EPM control class
-
-#ifndef __AP_EPM_h__
-#define __AP_EPM_h__
+#pragma once
 
 #include <AP_Math/AP_Math.h>
 #include <AP_Common/AP_Common.h>
@@ -71,5 +69,3 @@ private:
     // internal variables
     uint32_t    _last_grab_or_release;
 };
-
-#endif /* _AP_EPM_H_ */