- Revert making bus_generic_add_child() the default for BUS_ADD_CHILD().

Instead, we want busses to explicitly specify an add_child routine if they
  want to support identify routines, but by default disallow having outside
  drivers add devices.
- Give smbus(4) an explicit bus_add_child() method.

Requested by:	imp

sys/dev/smbus/smbus.c

@@ -56,6 +56,7 @@ static device_method_t smbus_methods[] = {
         DEVMETHOD(device_detach,        smbus_detach),
 
         /* bus interface */
+	DEVMETHOD(bus_add_child,	bus_generic_add_child),
         DEVMETHOD(bus_print_child,	bus_generic_print_child),
 
         { 0, 0 }

sys/kern/bus_if.m

@@ -194,7 +194,7 @@ METHOD device_t add_child {
 	int _order;
 	const char *_name;
 	int _unit;
-} DEFAULT bus_generic_add_child;
+};
 
 /**
  * @brief Allocate a system resource