dt-bindindgs: i2c: qcom,i2c-geni: document operating-points-v2

Just like other Geni serial interfaces (qcom,geni-spi and
qcom,geni-uart), the Geni I2C Controller comes with OPP table:

  sdm845-sony-xperia-tama-apollo.dtb: i2c@894000: Unevaluated properties are not allowed ('operating-points-v2' was unexpected)

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230113144950.78246-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Rob Herring <robh@kernel.org>