dt-bindings: display: xilinx: Fix example with psgtr

Commit cea0f76a483d ("dt-bindings: phy: Add DT bindings for Xilinx ZynqMP
PSGTR PHY") clearly defines #phy-cells as 4. In past 5 cells were used by
it never went to upstream. That's why fix example by using only 4 cells
instead of 5.

Fixes: e7c7970a678d ("dt-bindings: display: xlnx: Add ZynqMP DP subsystem bindings")
Signed-off-by: Michal Simek <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Link: https://lore.kernel.org/r/a291[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/display/xlnx/xlnx,zynqmp-dpsub.yaml

···
                <&xlnx_dpdma 2>,
                <&xlnx_dpdma 3>;
 
-        phys = <&psgtr 1 PHY_TYPE_DP 0 3 27000000>,
-               <&psgtr 0 PHY_TYPE_DP 1 3 27000000>;
+        phys = <&psgtr 1 PHY_TYPE_DP 0 3>,
+               <&psgtr 0 PHY_TYPE_DP 1 3>;
 
         phy-names = "dp-phy0", "dp-phy1";
     };