Fix libata docbook warnings.

Warning(linux-2.6.23-git8//drivers/ata/libata-scsi.c:3251): No description found for parameter 'dev'
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>