dt-bindings: pwm: Add MediaTek display PWM bindings

Add MT2701 compatible string.
Signed-off-by: NWeiqing Kong <weiqing.kong@mediatek.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/pwm-mtk-disp.txt

@@ -2,8 +2,9 @@ MediaTek display PWM controller
 
 Required properties:
  - compatible: should be "mediatek,<name>-disp-pwm":
-   - "mediatek,mt8173-disp-pwm": found on mt8173 SoC.
+   - "mediatek,mt2701-disp-pwm": found on mt2701 SoC.
    - "mediatek,mt6595-disp-pwm": found on mt6595 SoC.
+   - "mediatek,mt8173-disp-pwm": found on mt8173 SoC.
  - reg: physical base address and length of the controller's registers.
  - #pwm-cells: must be 2. See pwm.txt in this directory for a description of
    the cell format.