dt-bindings: interconnect: Update property for icc-rpm path tag

To support path tag in icc-rpm driver, the "#interconnect-cells"
property is updated as enumerate values: 1 or 2.  Setting to 1 means
it is compatible with old DT binding that interconnect path only
contains node id; if set to 2 for "#interconnect-cells" property, then
the second specifier is used as a tag (e.g. vote for which buckets).

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220712015929.2789881-2-leo.yan@linaro.org
Signed-off-by: Georgi Djakov <djakov@kernel.org>

Documentation/devicetree/bindings/interconnect/qcom,rpm.yaml

@@ -45,7 +45,11 @@ properties:
       - qcom,sdm660-snoc
 
   '#interconnect-cells':
-    const: 1
+    description: |
+      Value: <1> is one cell in an interconnect specifier for the
+      interconnect node id, <2> requires the interconnect node id and an
+      extra path tag.
+    enum: [ 1, 2 ]
 
   clocks:
     minItems: 2