libsas: use ata_is_ncq() and ata_has_dma() accessors

Use accessors instead of the raw protocol value.

Signed-off-by: Hannes Reinecke <hare@suse.com>
[hch: trivial cleanup of the ata_task assignments]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tejun Heo <tj@kernel.org>