include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/gsm/tlv.h b/include/osmocom/gsm/tlv.h
index a70b0f9..fda1810 100644
--- a/include/osmocom/gsm/tlv.h
+++ b/include/osmocom/gsm/tlv.h
@@ -1,5 +1,4 @@
-#ifndef _TLV_H
-#define _TLV_H
+#pragma once
 
 #include <stdint.h>
 #include <string.h>
@@ -435,5 +434,3 @@
 }
 
 /*! @} */
-
-#endif /* _TLV_H */