include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/gsmtap.h b/include/osmocom/core/gsmtap.h
index 4694219..69bd108 100644
--- a/include/osmocom/core/gsmtap.h
+++ b/include/osmocom/core/gsmtap.h
@@ -1,5 +1,4 @@
-#ifndef _GSMTAP_H
-#define _GSMTAP_H
+#pragma once
 
 /* gsmtap header, pseudo-header in front of the actua GSM payload */
 
@@ -239,5 +238,3 @@
 	uint8_t res;		/* reserved for future use (RFU) */
 
 } __attribute__((packed));
-
-#endif /* _GSMTAP_H */