adb: Correct class size on TYPE_ADB_DEVICE

The TypeInfo incorrectly just lets the class size be inherited.  It won't
actually break things, since the class is abstract, but we should get it
right.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

hw/input/adb.c

@@ -309,6 +309,7 @@ static void adb_device_class_init(ObjectClass *oc, void *data)
 static const TypeInfo adb_device_type_info = {
     .name = TYPE_ADB_DEVICE,
     .parent = TYPE_DEVICE,
+    .class_size = sizeof(ADBDeviceClass),
     .instance_size = sizeof(ADBDevice),
     .abstract = true,
     .class_init = adb_device_class_init,