dt-bindings: mfd: syscon: Add APM poweroff mailbox

Add compatible for an already used syscon poweroff/mailbox block in APM.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240627-dt-bindings-mfd-syscon-split-v4-7-dc6699a9f3e4@linaro.org
Signed-off-by: Lee Jones <lee@kernel.org>

Author: krzk

Documentation/devicetree/bindings/mfd/syscon.yaml

@@ -41,6 +41,8 @@ select:
           - amlogic,meson8b-analog-top
           - amlogic,meson8-pmu
           - amlogic,meson8b-pmu
+          - apm,merlin-poweroff-mailbox
+          - apm,mustang-poweroff-mailbox
           - apm,xgene-csw
           - apm,xgene-efuse
           - apm,xgene-mcb
@@ -134,6 +136,8 @@ properties:
           - amlogic,meson8b-analog-top
           - amlogic,meson8-pmu
           - amlogic,meson8b-pmu
+          - apm,merlin-poweroff-mailbox
+          - apm,mustang-poweroff-mailbox
           - apm,xgene-csw
           - apm,xgene-efuse
           - apm,xgene-mcb