include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/vty/telnet_interface.h b/include/osmocom/vty/telnet_interface.h
index 3c22201..e939ec7 100644
--- a/include/osmocom/vty/telnet_interface.h
+++ b/include/osmocom/vty/telnet_interface.h
@@ -18,8 +18,7 @@
  *
  */
 
-#ifndef TELNET_INTERFACE_H
-#define TELNET_INTERFACE_H
+#pragma once
 
 #include <osmocom/core/logging.h>
 #include <osmocom/core/select.h>
@@ -52,5 +51,3 @@
 void telnet_exit(void);
 
 /*! @} */
-
-#endif /* TELNET_INTERFACE_H */