include: Switch to #pragma once pattern

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/crypt/auth.h b/include/osmocom/crypt/auth.h
index 871e7c8..bed48e7 100644
--- a/include/osmocom/crypt/auth.h
+++ b/include/osmocom/crypt/auth.h
@@ -1,5 +1,4 @@
-#ifndef _OSMOCRYPTO_AUTH_H
-#define _OSMOCRYPTO_AUTH_H
+#pragma once
 
 /*! \addtogroup auth
  *  @{
@@ -96,6 +95,4 @@
 const char *osmo_auth_alg_name(enum osmo_auth_algo alg);
 enum osmo_auth_algo osmo_auth_alg_parse(const char *name);
 
-#endif /* _OSMOCRYPTO_AUTH_H */
-
 /* @} */