dt-bindings: display: mediatek: ethdr: Add compatible for MT8188

Add compatible name for MediaTek MT8188 ETHDR.
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: Hsiao Chien Sung <shawn.sung@mediatek.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Documentation/devicetree/bindings/display/mediatek/mediatek,ethdr.yaml

@@ -23,7 +23,11 @@ description:
 
 properties:
   compatible:
-    const: mediatek,mt8195-disp-ethdr
+    oneOf:
+      - const: mediatek,mt8195-disp-ethdr
+      - items:
+          - const: mediatek,mt8188-disp-ethdr
+          - const: mediatek,mt8195-disp-ethdr
 
   reg:
     maxItems: 7