include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/bitvec.h b/include/osmocom/core/bitvec.h
index 9c000d0..3138226 100644
--- a/include/osmocom/core/bitvec.h
+++ b/include/osmocom/core/bitvec.h
@@ -1,5 +1,4 @@
-#ifndef _BITVEC_H
-#define _BITVEC_H
+#pragma once
 
 /* bit vector utility routines */
 
@@ -66,5 +65,3 @@
 int bitvec_spare_padding(struct bitvec *bv, unsigned int up_to_bit);
 
 /*! @} */
-
-#endif /* _BITVEC_H */