ACPI / PM: Use target_state to set the device power state

Commit 20dacb71 ("ACPI / PM: Rework device power management to follow
ACPI 6") changed the device power management to use D3hot if the device
in question does not have _PR3 method even if D3cold was requested by the
caller.

However, if the device has _PR3 device->power.state is also set to D3hot
instead of D3Cold after power resources have been turned off because
device->power.state will be assigned from "state" instead of
"target_state".

Next time the device is transitioned to D0, acpi_power_transition() will
find that the current power state of the device is D3hot instead of D3cold
which causes it to power down all resources required for the current
(wrong) state D3hot.

Below is a simplified ASL example of a real touch panel device which
triggers the problem:

  Scope (TPL1)
  {
      Name (_PR0, Package (1) { \_SB.PCI0.I2C1.PXTC })
      Name (_PR3, Package (1) { \_SB.PCI0.I2C1.PXTC })
      ...
  }

In both D0 and D3hot the same power re...