PCI: rockchip: Control vpcie0v9 for system PM

vpcie0v9 is used for PHY, so we could disable it as we don't need PHY to
work then in S3 if folks assign it DT.  But we should note that there is a
side effect that we could not support beacon wakeup if we disable vpcie0v9
for aggressive power-saving.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Brian Norris <briannorris@chromium.org>
Cc: Jeffy Chen <jeffy.chen@rock-chips.com>