dt-bindings: pci: add PHY properties to Armada 7K/8K controller bindings

Armada CP110 PCIe controller can have from one to four PHYs for
configuring SERDES lanes (PCIe x1, PCIe x2 or PCIe x4). Describe the
phys and phy-names properties in the bindings.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

Documentation/devicetree/bindings/pci/pci-armada8k.txt

@@ -17,6 +17,14 @@ Required properties:
    name must be "core" for the first clock and "reg" for the second
    one
 
+Optional properties:
+- phys: phandle(s) to PHY node(s) following the generic PHY bindings.
+	Either 1, 2 or 4 PHYs might be needed depending on the number of
+	PCIe lanes.
+- phy-names: names of the PHYs corresponding to the number of lanes.
+	Must be "cp0-pcie0-x4-lane0-phy", "cp0-pcie0-x4-lane1-phy" for
+	2 PHYs.
+
 Example:
 
 	pcie@f2600000 {