testsuites/samples: Address unused parameter warnings

Add "(void) param;" annotation to address unused parameter warnings.
Found with GCC's warning -Wunused-parameter.

testsuites/samples/base_mp/initimpl.h

@@ -45,6 +45,8 @@ rtems_task Init(
   rtems_task_argument argument
 )
 {
+  (void) argument;
+
   rtems_name        task_name;
   rtems_id          tid;
   rtems_status_code status;