This patch refactors existing virtio-scsi code into VirtIOSCSICommon
in order to allow virtio_scsi_init_common() to be used by both internal
virtio_scsi_init() and external vhost-scsi-pci code.
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Asias He <asias@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>