include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/select.h b/include/osmocom/core/select.h
index efdd716..b6b9e82 100644
--- a/include/osmocom/core/select.h
+++ b/include/osmocom/core/select.h
@@ -1,5 +1,4 @@
-#ifndef _BSC_SELECT_H
-#define _BSC_SELECT_H
+#pragma once
 
 #include <osmocom/core/linuxlist.h>
 
@@ -41,5 +40,3 @@
 int osmo_select_main(int polling);
 
 /*! @} */
-
-#endif /* _BSC_SELECT_H */