include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/gsm/protocol/gsm_08_08.h b/include/osmocom/gsm/protocol/gsm_08_08.h
index 6b8f935..bf408eb 100644
--- a/include/osmocom/gsm/protocol/gsm_08_08.h
+++ b/include/osmocom/gsm/protocol/gsm_08_08.h
@@ -1,7 +1,6 @@
 /* From GSM08.08 */
 
-#ifndef GSM_0808_H
-#define GSM_0808_H
+#pragma once
 
 #include <stdlib.h>
 
@@ -299,5 +298,3 @@
 	GSM0808_PERM_HR2	= GSM0808_PERM_FR2 | 0x4,
 	GSM0808_PERM_HR3	= GSM0808_PERM_FR3 | 0x4,
 };
-
-#endif