virtio-net: Initialize hash reporting values

virtio-net: Initialize hash reporting values

The specification says hash_report should be set to
VIRTIO_NET_HASH_REPORT_NONE if VIRTIO_NET_F_HASH_REPORT is negotiated
but not configured with VIRTIO_NET_CTRL_MQ_RSS_CONFIG. However,
virtio_net_receive_rcu() instead wrote out the content of the extra_hdr
variable, which is not uninitialized in such a case.

Fix this by zeroing the extra_hdr.

Fixes: e22f0603fb2f ("virtio-net: reference implementation of hash report")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>