virtio_mmio: add support to set IRQ of a virtio device as wakeup source

According to virtio_mmio wakeup flag in device trees, set its IRQ
as wakeup source in virtqueue initialization.

Signed-off-by: Minghao Xue <quic_mingxue@quicinc.com>
Message-Id: <1654851507-13891-3-git-send-email-quic_mingxue@quicinc.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>