qdev: relax bus type check in qdev_device_add() (v2)

We are currently checking for an exact type match.  Use QOM dynamic_cast to
check for a compatible type instead.

Cc: Konrad Frederic <fred.konrad@greensocs.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
---
v1 -> v2:
 - also add cast to qbus_find_recursive (Peter)
 - simplify by doing object_dynamic_cast instead of messing with classes

hw/qdev-monitor.c

@@ -289,8 +289,7 @@ static BusState *qbus_find_recursive(BusState *bus, const char *name,
     if (name && (strcmp(bus->name, name) != 0)) {
         match = 0;
     }
-    if (bus_typename &&
-        (strcmp(object_get_typename(OBJECT(bus)), bus_typename) != 0)) {
+    if (bus_typename && !object_dynamic_cast(OBJECT(bus), bus_typename)) {
         match = 0;
     }
     if (match) {
@@ -435,7 +434,7 @@ DeviceState *qdev_device_add(QemuOpts *opts)
         if (!bus) {
             return NULL;
         }
-        if (strcmp(object_get_typename(OBJECT(bus)), k->bus_type) != 0) {
+        if (!object_dynamic_cast(OBJECT(bus), k->bus_type)) {
             qerror_report(QERR_BAD_BUS_FOR_DEVICE,
                           driver, object_get_typename(OBJECT(bus)));
             return NULL;