dt-bindings: display: mediatek: rdma: Add compatible for MediaTek MT6795

Add a compatible string for MediaTek Helio X10 MT6795's RDMA block: this
is the same as MT8173.

Signed-off-by: AngeloGioacchino Del Regno <[e-mail]>
Acked-by: Krzysztof Kozlowski <[e-mail]>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/[e-mail]/
Signed-off-by: Chun-Kuang Hu <[e-mail]>

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

···
           - const: mediatek,mt2701-disp-rdma
       - items:
           - enum:
+              - mediatek,mt6795-disp-rdma
+          - const: mediatek,mt8173-disp-rdma
+      - items:
+          - enum:
               - mediatek,mt8186-disp-rdma
               - mediatek,mt8192-disp-rdma
           - const: mediatek,mt8183-disp-rdma