virtio-scsi: use virtqueue_map_sg() when loading requests

virtio-scsi: use virtqueue_map_sg() when loading requests

The VirtQueueElement struct is serialized during migration but the
in_sg[]/out_sg[] iovec arrays are not usable on the destination host
because the pointers are meaningless.

Use virtqueue_map_sg() to refresh in_sg[]/out_sg[] to valid pointers
based on in_addr[]/out_addr[] hwaddrs.

Cc: Paolo Bonzini <[email protected]>
Signed-off-by: Stefan Hajnoczi <[email protected]>
Message-Id: <1438262173[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>