pci: layerscape: add pci driver based on DM

There are more than five kinds of Layerscape SoCs. unfortunately,
PCIe controller of each SoC is a little bit different. In order
to avoid too many macro definitions, the patch addes a new
implementation of PCIe driver based on DM. PCIe dts node is
used to describe the difference.

Signed-off-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 275b29b..692a398 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -71,4 +71,12 @@
 	  Enable support for the Xilinx AXI bridge for PCI express, an IP block
 	  which can be used on some generations of Xilinx FPGAs.
 
+config PCIE_LAYERSCAPE
+	bool "Layerscape PCIe support"
+	depends on DM_PCI
+	help
+	  Support Layerscape PCIe. The Layerscape SoC may have one or several
+	  PCIe controllers. The PCIe may works in RC or EP mode according to
+	  RCW[HOST_AGT_PEX] setting.
+
 endif