include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/timer_compat.h b/include/osmocom/core/timer_compat.h
index d86c109..fb2967b 100644
--- a/include/osmocom/core/timer_compat.h
+++ b/include/osmocom/core/timer_compat.h
@@ -26,8 +26,7 @@
  *  \brief Compatibility header with some helpers
  */
 
-#ifndef TIMER_COMPAT_H
-#define TIMER_COMPAT_H
+#pragma once
 
 
 /* Convenience macros for operations on timevals.
@@ -75,5 +74,3 @@
 
 
 /*! @} */
-
-#endif /* TIMER_COMPAT_H */