r8169: use pci_prepare_to_sleep in rtl_shutdown

r8169: use pci_prepare_to_sleep in rtl_shutdown

Use pci_prepare_to_sleep() like PCI core does in pci_pm_suspend_noirq.
This aligns setting a low-power mode during shutdown with the handling
of the transition to system suspend. Also the transition to runtime
suspend uses pci_target_state() instead of setting D3hot unconditionally.

Note: pci_prepare_to_sleep() uses device_may_wakeup() to check whether
      device may generate wakeup events. So we don't lose anything by
      not passing tp->saved_wolopts any longer.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/f573fdbd-ba6d-41c1-b68f-311d3c88db2c@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>