No need to call a function to avoid a warning.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index 88616d6..2797c14 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -629,7 +629,7 @@
 
     /* Avoid "unused static function" warning in configurations without
      * symmetric crypto. */
-    (void) mbedtls_timing_hardclock( );
+    (void) mbedtls_timing_hardclock;
 
 #if defined(MBEDTLS_MD5_C)
     if( todo.md5 )