include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/gsm/gsm0808.h b/include/osmocom/gsm/gsm0808.h
index 5127c00..a7e102c 100644
--- a/include/osmocom/gsm/gsm0808.h
+++ b/include/osmocom/gsm/gsm0808.h
@@ -17,8 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  */
-#ifndef OSMOCORE_GSM0808_H
-#define OSMOCORE_GSM0808_H
+#pragma once
 
 #include "tlv.h"
 
@@ -47,5 +46,3 @@
 
 const char *gsm0808_bssmap_name(uint8_t msg_type);
 const char *gsm0808_bssap_name(uint8_t msg_type);
-
-#endif