dt-bindings: net: qcom,ipa: add optional qcom,qmp property

For some systems, the IPA driver must make a request to ensure that
its registers are retained across power collapse of the IPA hardware.
On such systems, we'll use the existence of the "qcom,qmp" property
as a signal that this request is required.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/qcom,ipa.yaml

@@ -107,6 +107,10 @@ properties:
           - const: imem
           - const: config
 
+  qcom,qmp:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: phandle to the AOSS side-channel message RAM
+
   qcom,smem-states:
     $ref: /schemas/types.yaml#/definitions/phandle-array
     description: State bits used in by the AP to signal the modem.
@@ -222,6 +226,8 @@ examples:
                                      "imem",
                                      "config";
 
+                qcom,qmp = <&aoss_qmp>;
+
                 qcom,smem-states = <&ipa_smp2p_out 0>,
                                    <&ipa_smp2p_out 1>;
                 qcom,smem-state-names = "ipa-clock-enabled-valid",