PCI/AER: Clear device status bits during ERR_COR handling

In case of correctable error, the Correctable Error Detected bit in the
Device Status register is set.  Clear it after handling the error.

Signed-off-by: Oza Pawandeep <poza@codeaurora.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>