libata-acpi: remove redundent code for power resource handling

With commit:
bc9b6407
ACPI / PM: Rework the handling of devices depending on power resources

The ACPI core now takes care of the power resources an acpi device
depends on in that when the power resources are turned on, any devices
that are bound to or in the dependent list of this acpi device will be
runtime resumed. So there is no need for ata acpi code to duplicate this
effort, and thus, the ata_acpi_(un)register_power_resource functions are
no longer needed.

The above commit thinks the scsi device is not bound to the acpi device,
so needs to be added to the dependent list. But actually, it is. So
there is no need to add it to the dependent list, or it will be runtime
resumed twice(though this wouldn't cause any problem).

This patch fixes it, and as a result, the
ata_acpi_(un)register_power_resource and ata_acpi_(un)bind functions
are removed.

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