scsi: Fix migration of scsi sense data

c5f52875 changed the size of sense array in vmstate_scsi_device by
mistake. This patch restores the old size, and add a subsection for the
remaining part of the buffer size. So that migration is not broken.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
virtio-scsi: actually honor sense_size from configuration space

We were always truncating the sense size to 96 bytes.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>