dt-bindings: display: mediatek: change to use enum for mutex

All single entry cases in mutex can be merged as a single enum.

Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20220406030009.2357-3-rex-bc.chen@mediatek.com/
Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

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

@@ -23,21 +23,15 @@ description: |
 
 properties:
   compatible:
-    oneOf:
-      - items:
-          - const: mediatek,mt2701-disp-mutex
-      - items:
-          - const: mediatek,mt2712-disp-mutex
-      - items:
-          - const: mediatek,mt8167-disp-mutex
-      - items:
-          - const: mediatek,mt8173-disp-mutex
-      - items:
-          - const: mediatek,mt8183-disp-mutex
-      - items:
-          - const: mediatek,mt8192-disp-mutex
-      - items:
-          - const: mediatek,mt8195-disp-mutex
+    enum:
+      - mediatek,mt2701-disp-mutex
+      - mediatek,mt2712-disp-mutex
+      - mediatek,mt8167-disp-mutex
+      - mediatek,mt8173-disp-mutex
+      - mediatek,mt8183-disp-mutex
+      - mediatek,mt8192-disp-mutex
+      - mediatek,mt8195-disp-mutex
+
   reg:
     maxItems: 1