hw/scsi/virtio-scsi.c: fix the "type" use error in virtio_scsi_handle_ctrl

The local variable "type" in virtio_scsi_handle_ctl represents the tmf
command type from the guest and it has the same meaning as the
req->req.tmf.type. However, before the invoking of virtio_scsi_parse_req
the req->req.tmf.type doesn't has the correct value(just initialized to
zero). Therefore, we need to use the "type" variable to judge the case.

Cc: qemu-stable@nongnu.org
Signed-off-by: Bin Wu <wu.wubin@huawei.com>
[Actually make it compile, "type" must be uint32_t in order to pass
 it to virtio_tswap32s. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
