ata: libata-core: Do not resume ports that have been runtime suspended

The scsi disk driver does not resume disks that have been runtime
suspended by the user. To be consistent with this behavior, do the same
for ata ports and skip the PM request in ata_port_pm_resume() if the
port was already runtime suspended. With this change, it is no longer
necessary to for the PM state of the port to ACTIVE as the PM core code
will take care of that when handling runtime resume.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>