TMXR: Accept names when establishing listen sockets as originally intended

Problem found while testing solution for the problem reported in #767

sim_tmxr.c

@@ -2745,9 +2745,11 @@ while (*tptr) {
                 else
                     if (0 == MATCH_CMD (cptr, "TELNET"))
                         listennotelnet = FALSE;
-                    else
+                    else {
+                        if (*tptr)
                             return sim_messagef (SCPE_ARG, "Invalid Specifier: %s\n", tptr);
                         }
+                }
             cptr = init_cptr;
             }
         cptr = get_glyph_nc (cptr, port, ';');