PCI: layerscape: Change default error response behavior

By default, when the PCIe controller experiences an erroneous completion
from an external completer for its outbound non-posted request, it sends
an OKAY response to the device's internal AXI slave system interface.
However, this default system error response behavior cannot be used for
other types of outbound non-posted requests.  For example, the outbound
memory read transaction requires an actual ERROR response, like UR
completion or completion timeout.

Fix this by forwarding the error response of the non-posted request.

Signed-off-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>