virtio-pci: decouple the single vector from the interrupt process

To reuse the interrupt process in configure interrupt
Need to decouple the single vector from the interrupt process. Add new function
kvm_virtio_pci_vector_use_one and _release_one. These functions are use
for the single vector, the whole process will finish in a loop for the vq number.

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