libata-link: add PMP related ATA constants
Tejun Heo authored

Add Port Multiplier related ATA constants and macros.  Some of these
will be used by ata_link implementation.
Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJeff Garzik <jeff@garzik.org>
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