libata: Limit ATAPI DMA to R/W commands only for TORiSAN DVD drives (take 3)

patch 4/4:

  Limit ATAPI DMA to R/W commands only for TORiSAN DRD-N216 DVD-ROM drives
  (http://bugzilla.kernel.org/show_bug.cgi?id=6710)

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>