dt-bindings: phy-rockchip-pcie: Convert to per-lane PHY model

Deprecate the legacy Rockchip PCIe PHY and encourage users to use per-lane
PHY mode by setting #phy-cells to 1.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/phy/rockchip-pcie-phy.txt

@@ -3,7 +3,6 @@ Rockchip PCIE PHY
 
 Required properties:
  - compatible: rockchip,rk3399-pcie-phy
- - #phy-cells: must be 0
  - clocks: Must contain an entry in clock-names.
 	See ../clocks/clock-bindings.txt for details.
  - clock-names: Must be "refclk"
@@ -11,6 +10,12 @@ Required properties:
 	See ../reset/reset.txt for details.
  - reset-names: Must be "phy"
 
+Required properties for legacy PHY mode (deprecated):
+ - #phy-cells: must be 0
+
+Required properties for per-lane PHY mode (preferred):
+ - #phy-cells: must be 1
+
 Example:
 
 grf: syscon@ff770000 {