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

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

Commit 9f2840365b4f ("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: 4cfc3e0a97ff ("dt-bindings: display: xlnx: Add ZynqMP DP subsystem bindings")
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/a291be294dea6e580ad9acd436742a48b7cd00a2.1634539210.git.michal.simek@xilinx.com
Signed-off-by: Rob Herring <robh@kernel.org>