include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/loggingrb.h b/include/osmocom/core/loggingrb.h
index a6f377b..acdccfb 100644
--- a/include/osmocom/core/loggingrb.h
+++ b/include/osmocom/core/loggingrb.h
@@ -1,5 +1,4 @@
-#ifndef _LOGGINGRB_H
-#define _LOGGINGRB_H
+#pragma once
 
 /* (C) 2012-2013 by Katerina Barone-Adesi <kat.obsc@gmail.com>
  * All Rights Reserved
@@ -36,5 +35,3 @@
 struct log_target *log_target_create_rb(size_t size);
 
 /*! @} */
-
-#endif /* _LOGGINGRB_H  */