dt-bindings: mailbox: Add compatible for the MSM8976

Add the mailbox compatible for the MSM8976 SoC.
Signed-off-by: Adam Skladowski <a39.skl@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

Documentation/devicetree/bindings/mailbox/qcom,apcs-kpss-global.yaml

@@ -21,6 +21,7 @@ properties:
       - qcom,msm8916-apcs-kpss-global
       - qcom,msm8939-apcs-kpss-global
       - qcom,msm8953-apcs-kpss-global
+      - qcom,msm8976-apcs-kpss-global
       - qcom,msm8994-apcs-kpss-global
       - qcom,msm8996-apcs-hmss-global
       - qcom,msm8998-apcs-hmss-global