hw/s390x/s390-virtio-ccw: Remove superfluous code to set the NIC model

The check for nd->model being NULL was originally required, but in
commit e11f463295d95aba ("s390x/virtio: use qemu_check_nic_model()")
the corresponding code had been replaced by a call to the function
qemu_check_nic_model() - and this in turn calls qemu_find_nic_model()
which contains the same check for nd->model being NULL again. So we
can remove this from the calling site now.

Message-Id: <20230804073525.11857-1-thuth@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/s390x/s390-virtio-ccw.c

@@ -222,10 +222,6 @@ static void s390_create_virtio_net(BusState *bus, const char *name)
         NICInfo *nd = &nd_table[i];
         DeviceState *dev;
 
-        if (!nd->model) {
-            nd->model = g_strdup("virtio");
-        }
-
         qemu_check_nic_model(nd, "virtio");
 
         dev = qdev_new(name);