spi: dt-bindings: qcom,spi-qcom-qspi: document OPP and power-domains

QSPI on Qualcomm SDM845, SC7180 and SC7280 SoCs uses OPP table (both in
DTS and Linux driver) and is suuplied by CX power domain.  Document
missing properties to fix:

  sc7280-idp2.dtb: spi@88dc000: Unevaluated properties are not allowed ('operating-points-v2', 'power-domains' were unexpected)
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230217155802.848178-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/qcom,spi-qcom-qspi.yaml

@@ -52,6 +52,11 @@ properties:
       - const: qspi-config
       - const: qspi-memory
 
+  operating-points-v2: true
+
+  power-domains:
+    maxItems: 1
+
 required:
   - compatible
   - reg