include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/conv.h b/include/osmocom/core/conv.h
index 4cc791f..e7f6bd6 100644
--- a/include/osmocom/core/conv.h
+++ b/include/osmocom/core/conv.h
@@ -28,8 +28,7 @@
  * Osmocom convolutional encoder and decoder
  */
 
-#ifndef __OSMO_CONV_H__
-#define __OSMO_CONV_H__
+#pragma once
 
 #include <stdint.h>
 
@@ -142,5 +141,3 @@
 
 
 /*! @} */
-
-#endif /* __OSMO_CONV_H__ */