pci: Add PCIe Gen4 controller driver for NXP Layerscape SoCs

Add PCIe Gen4 driver for the NXP Layerscape SoCs. This PCIe
controller is based on the Mobiveil IP, which is compatible
with the PCI Express™ Base Specification, Revision 4.0.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Bao Xiaowei <Xiaowei.Bao@nxp.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 1521885..763bd50 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -105,6 +105,14 @@
 	  PCIe controllers. The PCIe may works in RC or EP mode according to
 	  RCW[HOST_AGT_PEX] setting.
 
+config PCIE_LAYERSCAPE_GEN4
+	bool "Layerscape Gen4 PCIe support"
+	depends on DM_PCI
+	help
+	  Support PCIe Gen4 on NXP Layerscape SoCs, which may have one or
+	  several PCIe controllers. The PCIe controller can work in RC or
+	  EP mode according to RCW[HOST_AGT_PEX] setting.
+
 config PCIE_INTEL_FPGA
 	bool "Intel FPGA PCIe support"
 	depends on DM_PCI