kconfig: add dependency PCIE_LAYERSCAPE_GEN4 for FSL_PCIE_COMPAT

The LX2160A PCIe is using driver PCIE_LAYERSCAPE_GEN4 instead
of PCIE_LAYERSCAPE.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>