PCI/portdrv: Disable port driver in compat mode

The "pcie_ports=compat" kernel parameter sets pcie_ports_disabled, which is
intended to disable the PCIe port driver.  But even when it was disabled,
we registered pcie_portdriver so we could work around a BIOS PME issue (see
fe31e697 ("PCI/PCIe: Clear Root PME Status bits early during system
resume")).

Registering the driver meant that the pcie_portdrv_probe() path called
pci_enable_device(), pci_save_state(), pm_runtime_set_autosuspend_delay(),
pm_runtime_use_autosuspend(), etc., even when the driver was disabled.

We've since moved the BIOS PME workaround from the port driver to the core,
so stop registering the PCIe port driver in compat mode.

This means "pcie_ports=compat" will now be basically the same as turning
off CONFIG_PCIEPORTBUS completely.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>