spapr-vty: Use TYPE_ definition instead of hardcoding

There's a call to object_dynamic_cast() in spapr_vty which uses the type
name "spapr-vty" directly, instead of the usual idiom of using the #defined
TYPE_VIO_SPAPR_VTY_DEVICE.  Fix it.
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NAlexander Graf <agraf@suse.de>

hw/char/spapr_vty.c

@@ -193,7 +193,7 @@ VIOsPAPRDevice *spapr_vty_get_default(VIOsPAPRBus *bus)
         DeviceState *iter = kid->child;
 
         /* Only look at VTY devices */
-        if (!object_dynamic_cast(OBJECT(iter), "spapr-vty")) {
+        if (!object_dynamic_cast(OBJECT(iter), TYPE_VIO_SPAPR_VTY_DEVICE)) {
             continue;
         }