include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/utils.h b/include/osmocom/core/utils.h
index 2333de6..c08e775 100644
--- a/include/osmocom/core/utils.h
+++ b/include/osmocom/core/utils.h
@@ -1,5 +1,4 @@
-#ifndef OSMOCORE_UTIL_H
-#define OSMOCORE_UTIL_H
+#pragma once
 
 #include <osmocom/core/backtrace.h>
 
@@ -62,5 +61,3 @@
 
 
 /*! @} */
-
-#endif