PCI: layerscape: Add LS1046a support

Add support for the LS1046a PCIe controller.  This device has a different
LUT_DBG offset, so add "lut_dbg" to ls_pcie_drvdata to
describe this difference.

[bhelgaas: changelog, remove now-unused PCIE_LUT_DBG]
Signed-off-by: Mingkai Hu <mingkai.hu@nxp.com>
Signed-off-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>