s390x: add property adapter_routes_max_batch

To make virtio-ccw supports more that  64 virtqueues we will have to
increase ADAPTER_ROUTES_MAX_GSI which is currently limiting the number if
possible adapter routes. Of course increasing the number of supported
routes can break backwards migration.

Let us introduce a compatibility property adapter_routes_max_batch so
client code can use the some old limit if in compatibility mode and
retain the migration compatibility.

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

include/hw/s390x/s390_flic.h

@@ -32,6 +32,8 @@ typedef struct AdapterRoutes {
 
 typedef struct S390FLICState {
     SysBusDevice parent_obj;
+    /* to limit AdapterRoutes.num_routes for compat */
+    uint32_t adapter_routes_max_batch;
 
 } S390FLICState;