PCI/AER: Factor out ERR_NONFATAL status bit clearing

aer_error_resume() clears all ERR_NONFATAL error status bits.  This is
exactly what pci_cleanup_aer_uncorrect_error_status(), so use that instead
of duplicating the code.

Signed-off-by: Oza Pawandeep <poza@codeaurora.org>
[bhelgaas: split to separate patch]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>