dt-bindings: display: mediatek: control dpi pins mode to avoid leakage

Add property "pinctrl-names" to swap pin mode between gpio and dpi mode.
Set the dpi pins to gpio mode and output-low to avoid leakage current
when dpi disabled.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Documentation/devicetree/bindings/display/mediatek/mediatek,dpi.txt

@@ -17,6 +17,9 @@ Required properties:
   Documentation/devicetree/bindings/graph.txt. This port should be connected
   to the input port of an attached HDMI or LVDS encoder chip.
 
+Optional properties:
+- pinctrl-names: Contain "default" and "sleep".
+
 Example:
 
 dpi0: dpi@1401d000 {
@@ -27,6 +30,9 @@ dpi0: dpi@1401d000 {
 		 <&mmsys CLK_MM_DPI_ENGINE>,
 		 <&apmixedsys CLK_APMIXED_TVDPLL>;
 	clock-names = "pixel", "engine", "pll";
+	pinctrl-names = "default", "sleep";
+	pinctrl-0 = <&dpi_pin_func>;
+	pinctrl-1 = <&dpi_pin_idle>;
 
 	port {
 		dpi0_out: endpoint {