include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/bits.h b/include/osmocom/core/bits.h
index 4c68532..d4ab505 100644
--- a/include/osmocom/core/bits.h
+++ b/include/osmocom/core/bits.h
@@ -1,5 +1,4 @@
-#ifndef _OSMO_BITS_H
-#define _OSMO_BITS_H
+#pragma once
 
 #include <stdint.h>
 
@@ -74,5 +73,3 @@
 void osmo_revbytebits_buf(uint8_t *buf, int len);
 
 /*! @} */
-
-#endif /* _OSMO_BITS_H */