PCI/AER: Add RCEC AER error injection support

Root Complex Event Collectors (RCEC) appear as peers to Root Ports and may
also have the AER capability.

Add RCEC support to the AER error injection driver.

Co-developed-by: Sean V Kelley <sean.v.kelley@intel.com>
Link: https://lore.kernel.org/r/20201121001036.8560-16-sean.v.kelley@intel.com
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> # non-native/no RCEC
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>