sata_promise: make pdc_atapi_pkt() use values from qc->tf

Make pdc_atapi_pkt() use values from qc->tf instead of creating its
own.  This is to ease future ATAPI handling changes.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Jeff Garzik <jeff@garzik.org>