libata-link: make two port flags HRST_TO_RESUME and SKIP_D2H_BSY link flags

HRST_TO_RESUME and SKIP_D2H_BSY are link attributes.  Move them to
ata_link->flags.  This will allow host and PMP links to have different
attributes.  ata_port_info->link_flags is added and used by LLDs to
specify these flags during initialization.

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