include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/msgb.h b/include/osmocom/core/msgb.h
index 33e8081..bf83d67 100644
--- a/include/osmocom/core/msgb.h
+++ b/include/osmocom/core/msgb.h
@@ -1,5 +1,4 @@
-#ifndef _MSGB_H
-#define _MSGB_H
+#pragma once
 
 /* (C) 2008 by Harald Welte <laforge@gnumonks.org>
  * All Rights Reserved
@@ -413,5 +412,3 @@
 void msgb_set_talloc_ctx(void *ctx);
 
 /*! @} */
-
-#endif /* _MSGB_H */