server: revert commit 7e6556b3ca

With the removal of old tpiu code, commit 7e6556b3ca ("server:
permit the add_service function to return the created service")
http://openocd.zylin.com/5717/ can be reverted.

Fix also the new calls to add_service().

Change-Id: Ib7f2dfc6a9e829239e20313e0f121911085fdc00
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6031
Tested-by: jenkins
Reviewed-by: Adrian M Negreanu <adrian.negreanu@nxp.com>

src/target/openrisc/jsp_server.c

@@ -207,8 +207,7 @@ int jsp_init(struct or1k_jtag *jtag_info, char *banner)
 		jsp_new_connection,
 		jsp_input,
 		jsp_connection_closed,
-		jsp_service,
-		NULL);
+		jsp_service);
 }
 
 COMMAND_HANDLER(handle_jsp_port_command)