hw/scsi-bus.c: Fix use of uninitialised variable

Don't use req before it has been initialised in scsi_req_new().
This fixes a compile failure due to gcc complaining about this.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

hw/scsi-bus.c

@@ -372,7 +372,7 @@ SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
     } else {
         trace_scsi_req_parsed(d->id, lun, tag, buf[0],
                               cmd.mode, cmd.xfer);
-        if (req->cmd.lba != -1) {
+        if (cmd.lba != -1) {
             trace_scsi_req_parsed_lba(d->id, lun, tag, buf[0],
                                       cmd.lba);
         }