dt-bindings: soc: qcom,smp2p: Mark qcom,ipc as deprecated

Deprecate the qcom,ipc way of accessing the mailbox in favor of the
'mboxes' property.

Update the example to use mboxes.
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Reviewed-by: "Rob Herring (Arm)" <robh@kernel.org>
Link: https://lore.kernel.org/r/20240425-qcom-ipc-deprecate-v1-2-a8d8034253ea@z3ntu.xyzSigned-off-by: Bjorn Andersson <andersson@kernel.org>

Documentation/devicetree/bindings/soc/qcom/qcom,smp2p.yaml

@@ -41,6 +41,7 @@ properties:
     description:
       Three entries specifying the outgoing ipc bit used for signaling the
       remote end of the smp2p edge.
+    deprecated: true
 
   qcom,local-pid:
     $ref: /schemas/types.yaml#/definitions/uint32
@@ -128,7 +129,7 @@ examples:
         compatible = "qcom,smp2p";
         qcom,smem = <431>, <451>;
         interrupts = <GIC_SPI 143 IRQ_TYPE_EDGE_RISING>;
-        qcom,ipc = <&apcs 8 18>;
+        mboxes = <&apcs 18>;
         qcom,local-pid = <0>;
         qcom,remote-pid = <4>;