ata: sata_dwc_460ex: don't call ata_sff_qc_issue() on DMA commands

ata_sff_qc_issue() can't handle DMA commands and thus we have to avoid it for
them. Do call ata_bmdma_qc_issue() instead for this case. Note that the former
one distinguishes PIO and DMA mode and behaves accordingly.

Suggested-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>