PCI: layerscape: Add "fsl,ls2085a-pcie" compatible ID

The Layerscape PCI host driver must recognize ls2085a compatible when using
firmware with ls2085a compatible property, otherwise the PCI bus won't be
detected even though ls2085a compatible is included by the dts.

Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>