[libata] pm: differentiate system and runtime pm for ata port

We need to do different things for system PM and runtime PM, e.g. we do
not need to enable runtime wake for ZPODD when we are doing system
suspend, etc.

Currently, we use PMSG_SUSPEND for both system suspend and runtime
suspend and PMSG_ON for both system resume and runtime resume. Change
this by using PMSG_AUTO_SUSPEND for runtime suspend and PMSG_AUTO_RESUME
for runtime resume. And since PMSG_ON means no transition, it is changed
to PMSG_RESUME for ata port's system resume.

The ata_acpi_set_state is modified accordingly, and the sata case and
pata case is seperated for easy reading.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>