dt-bindings: PCI: keystone: Add bindings to get device control module

Add bindings to get device control module which has the device id and
vendor id to be configured in the keystone PCIe controller.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pci/pci-keystone.txt

@@ -19,6 +19,9 @@ pcie_msi_intc : Interrupt controller device node for MSI IRQ chip
 	interrupt-cells: should be set to 1
 	interrupts: GIC interrupt lines connected to PCI MSI interrupt lines
 
+ti,syscon-pcie-id : phandle to the device control module required to set device
+		    id and vendor id.
+
  Example:
 	pcie_msi_intc: msi-interrupt-controller {
 			interrupt-controller;