trace, RAS: Replace bare numbers with #defines for PCIe AER error strings

Replace bare numbers like "BIT(0)" with the existing #defines, e.g.,
PCI_ERR_COR_RCVR, to improve maintainability.  This way grep will find more
uses of the #defines.

No functional change.

[bhelgaas: changelog]
Signed-off-by: Chen, Gong <gong.chen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>