vhost: claim support of guest announce

It's actually a feature already enabled in Linux kernel (since v3.5).
What we need to do is simply to claim that we support such feature,
and nothing else.

With that, the guest will send an ARP message after live migration
to notify the switches about the new location of migrated VM.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Tested-by: Pavel Fedin <p.fedin@samsung.com>

lib/librte_vhost/virtio-net.c

@@ -74,6 +74,7 @@ static struct virtio_net_config_ll *ll_root;
 #define VHOST_SUPPORTED_FEATURES ((1ULL << VIRTIO_NET_F_MRG_RXBUF) | \
 				(1ULL << VIRTIO_NET_F_CTRL_VQ) | \
 				(1ULL << VIRTIO_NET_F_CTRL_RX) | \
+				(1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE) | \
 				(VHOST_SUPPORTS_MQ)            | \
 				(1ULL << VIRTIO_F_VERSION_1)   | \
 				(1ULL << VHOST_F_LOG_ALL)      | \