dt-bindings: mailbox: qcom,apcs-kpss-global: Add syscon const for relevant entries

msm8916, msm8939, msm8953, msm8994 and qcs404 already declare or should
declare syscon as they have drivers that use syscon inside of the apcs-kpss
block.

grep apcs arch/arm64/boot/dts/qcom/* | grep syscon

Add in the additional syscon in the documentation for the above mentioned
parts.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

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

@@ -15,26 +15,30 @@ maintainers:
 
 properties:
   compatible:
-    enum:
-      - qcom,ipq6018-apcs-apps-global
-      - qcom,ipq8074-apcs-apps-global
-      - 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
-      - qcom,qcm2290-apcs-hmss-global
-      - qcom,qcs404-apcs-apps-global
-      - qcom,sc7180-apss-shared
-      - qcom,sc8180x-apss-shared
-      - qcom,sdm660-apcs-hmss-global
-      - qcom,sdm845-apss-shared
-      - qcom,sm6125-apcs-hmss-global
-      - qcom,sm6115-apcs-hmss-global
-      - qcom,sm8150-apss-shared
-
+    oneOf:
+      - items:
+          - enum:
+              - qcom,ipq6018-apcs-apps-global
+              - qcom,ipq8074-apcs-apps-global
+              - qcom,msm8976-apcs-kpss-global
+              - qcom,msm8996-apcs-hmss-global
+              - qcom,msm8998-apcs-hmss-global
+              - qcom,qcm2290-apcs-hmss-global
+              - qcom,sc7180-apss-shared
+              - qcom,sc8180x-apss-shared
+              - qcom,sdm660-apcs-hmss-global
+              - qcom,sdm845-apss-shared
+              - qcom,sm6125-apcs-hmss-global
+              - qcom,sm6115-apcs-hmss-global
+              - qcom,sm8150-apss-shared
+      - items:
+          - enum:
+              - qcom,msm8916-apcs-kpss-global
+              - qcom,msm8939-apcs-kpss-global
+              - qcom,msm8953-apcs-kpss-global
+              - qcom,msm8994-apcs-kpss-global
+              - qcom,qcs404-apcs-apps-global
+          - const: syscon
   reg:
     maxItems: 1
 
@@ -121,7 +125,7 @@ examples:
     #define GCC_APSS_AHB_CLK_SRC  1
     #define GCC_GPLL0_AO_OUT_MAIN 123
     apcs: mailbox@b011000 {
-        compatible = "qcom,qcs404-apcs-apps-global";
+        compatible = "qcom,qcs404-apcs-apps-global", "syscon";
         reg = <0x0b011000 0x1000>;
         #mbox-cells = <1>;
         clocks = <&apcs_hfpll>, <&gcc GCC_GPLL0_AO_OUT_MAIN>;