PCI/AER: Set dev->__aer_firmware_first only for matching devices

Previously, we always updated info->firmware_first, even for HEST entries
that didn't match the device.  Therefore, if the last HEST descriptor was
a PCIe structure that didn't match the device, we always cleared
dev->__aer_firmware_first.

Tested-by: Betty Dall <betty.dall@hp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>