PCI: layerscape: Add support for ls2088a

The ls2088a PCIe controller's register addresses are different from
ls2080a, so add a match entry to identify ls2088a PCIe.

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