virtio-net: add support for configure interrupt

Add functions to support configure interrupt in virtio_net
The functions are config_pending and config_mask, while
this input idx is VIRTIO_CONFIG_IRQ_IDX will check the
function of configure interrupt.

Signed-off-by: Cindy Lu <lulu@redhat.com>
Message-Id: <20211104164827.21911-9-lulu@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
4 files changed