systemc: Add a "kind()" overload to sc_port_base.

This is "implementation defined" but needs to exist to match the
golden reference output from Accellera.

Change-Id: I9b7949343b7c62a8d568abc06ab4dfc88233b20a
Reviewed-on: https://gem5-review.googlesource.com/c/12621
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/systemc/ext/core/sc_port.hh

@@ -68,6 +68,8 @@ class sc_port_base : public sc_object
     int maxSize() const;
     int size() const;
 
+    const char *kind() const { return "sc_port_base"; }
+
   protected:
     // Implementation defined, but depended on by the tests.
     void bind(sc_interface &);