[SCSI] storvsc: NULL pointer dereference fix

[SCSI] storvsc: NULL pointer dereference fix

If the initialization of storvsc fails, the storvsc_device_destroy()
causes NULL pointer dereference.

storvsc_bus_scan()
  scsi_scan_target()
    __scsi_scan_target()
      scsi_probe_and_add_lun(hostdata=NULL)
        scsi_alloc_sdev(hostdata=NULL)

	  sdev->hostdata = hostdata

	  now the host allocation fails

          __scsi_remove_device(sdev)

	  calls sdev->host->hostt->slave_destroy() ==
	  storvsc_device_destroy(sdev)
	    access of sdev->hostdata->request_mempool

Signed-off-by: Ales Novak <[email protected]>
Signed-off-by: Thomas Abraham <[email protected]>
Reviewed-by: Jiri Kosina <[email protected]>
Acked-by: K. Y. Srinivasan <[email protected]>
Cc: [email protected]
Signed-off-by: James Bottomley <[email protected]>