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

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.org
Signed-off-by: Mark Brown <broonie@kernel.org>