libata: make gtf_filter per-dev

Add ->gtf_filter to ata_device and set it to ata_acpi_gtf_filter when
initializing ata_link.  This is to allow quirks which apply different
gtf filters.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>