virtio-net: mac property is mandatory

Mac feature bit isn't going to work as all network cards already have a
'mac' property to set the mac address.  Remove it from mask and add in
get_features.

Reported-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/virtio-net.c

@@ -151,6 +151,8 @@ static uint32_t virtio_net_get_features(VirtIODevice *vdev, uint32_t features)
 {
     VirtIONet *n = to_virtio_net(vdev);
 
+    features |= (1 << VIRTIO_NET_F_MAC);
+
     if (peer_has_vnet_hdr(n)) {
         tap_using_vnet_hdr(n->nic->nc.peer, 1);
     } else {

hw/virtio-net.h

@@ -157,7 +157,6 @@ struct virtio_net_ctrl_mac {
         DEFINE_VIRTIO_COMMON_FEATURES(_state, _field), \
         DEFINE_PROP_BIT("csum", _state, _field, VIRTIO_NET_F_CSUM, true), \
         DEFINE_PROP_BIT("guest_csum", _state, _field, VIRTIO_NET_F_GUEST_CSUM, true), \
-        DEFINE_PROP_BIT("mac", _state, _field, VIRTIO_NET_F_MAC, true), \
         DEFINE_PROP_BIT("gso", _state, _field, VIRTIO_NET_F_GSO, true), \
         DEFINE_PROP_BIT("guest_tso4", _state, _field, VIRTIO_NET_F_GUEST_TSO4, true), \
         DEFINE_PROP_BIT("guest_tso6", _state, _field, VIRTIO_NET_F_GUEST_TSO6, true), \