dt-bindings: mailbox: mediatek,gce-mailbox: add mt8188 compatible name

Add mt8188 compatible name.
Signed-off-by: Elvis Wang <Elvis.Wang@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno<angelogioacchino.delregno@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

Documentation/devicetree/bindings/mailbox/mediatek,gce-mailbox.yaml

@@ -21,6 +21,7 @@ properties:
       - mediatek,mt8173-gce
       - mediatek,mt8183-gce
       - mediatek,mt8186-gce
+      - mediatek,mt8188-gce
       - mediatek,mt8192-gce
       - mediatek,mt8195-gce