[PATCH] libata: kill @cdb argument from xlat methods

xlat function will be updated to consider qc->scsicmd->cmd_len and
many xlat functions deference qc->scsicmd already.  It doesn't make
sense to pass qc->scsicmd->cmnd as @cdb separately.  Kill the
argument.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>