include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/gsm/gsm0502.h b/include/osmocom/gsm/gsm0502.h
index 46b629e..6ee5a60 100644
--- a/include/osmocom/gsm/gsm0502.h
+++ b/include/osmocom/gsm/gsm0502.h
@@ -1,5 +1,4 @@
-#ifndef OSMOCOM_GSM_0502_H
-#define OSMOCOM_GSM_0502_H
+#pragma once
 
 #include <stdint.h>
 
@@ -34,5 +33,3 @@
 
 unsigned int
 gsm0502_calc_paging_group(struct gsm48_control_channel_descr *chan_desc, uint64_t imsi);
-
-#endif