PCI/AER: Clear AER status from Root Port when resetting Downstream Port

PCI/AER: Clear AER status from Root Port when resetting Downstream Port

The pci_dev parameter given to aer_root_reset() may be a Downstream Port
rather than the Root Port. Get the Root Port from the provided device in
order to clear the root's AER status.

Link: https://lore.kernel.org/r/20210104230300.1277180-3-kbusch@kernel.org
Tested-by: Hedi Berriche <hedi.berriche@hpe.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Sean V Kelley <sean.v.kelley@intel.com>
Acked-by: Hedi Berriche <hedi.berriche@hpe.com>