dt-bindings: PCI: cadence: Add DT bindings for optional PHYs

Update DT documentation to include optional PHYs for cadence PCIe
host and endpoint controllers.

Signed-off-by: Alan Douglas <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/pci/cdns,cdns-pcie-ep.txt

···
 
 Optional properties:
 - max-functions: Maximum number of functions that can be configured (default 1).
+- phys: From PHY bindings: List of Generic PHY phandles. One per lane if more
+  than one in the list.  If only one PHY listed it must manage all lanes. 
+- phy-names:  List of names to identify the PHY.
 
 Example:
 
···
 	reg-names = "reg", "mem";
 	cdns,max-outbound-regions = <16>;
 	max-functions = /bits/ 8 <8>;
+	phys = <&ep_phy0 &ep_phy1>;
+	phy-names = "pcie-lane0","pcie-lane1";
 };

Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.txt

···
   translations (default 32)
 - vendor-id: The PCI vendor ID (16 bits, default is design dependent)
 - device-id: The PCI device ID (16 bits, default is design dependent)
+- phys: From PHY bindings: List of Generic PHY phandles. One per lane if more
+  than one in the list.  If only one PHY listed it must manage all lanes. 
+- phy-names:  List of names to identify the PHY.
 
 Example:
 
···
 	interrupt-map-mask = <0x0 0x0 0x0  0x7>;
 
 	msi-parent = <&its_pci>;
+
+	phys = <&pcie_phy0>;
+	phy-names = "pcie-phy";
 };