drm/mediatek: update dt-bindings for mt2712

Update device tree binding documentation for the display subsystem for
Mediatek MT2712 SoCs.

Signed-off-by: Stu Hsieh <stu.hsieh@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: CK Hu <ck.hu@mediatek.com>

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

@@ -40,7 +40,7 @@ Required properties (all function blocks):
 	"mediatek,<chip>-dpi"        - DPI controller, see mediatek,dpi.txt
 	"mediatek,<chip>-disp-mutex" - display mutex
 	"mediatek,<chip>-disp-od"    - overdrive
-  the supported chips are mt2701 and mt8173.
+  the supported chips are mt2701, mt2712 and mt8173.
 - reg: Physical base address and length of the function block register space
 - interrupts: The interrupt signal from the function block (required, except for
   merge and split function blocks).