regulator: dt-bindings: qcom,rpmh: document vdd-l7-bob-supply on PMR735A

The PMR735A comes with vdd-l7-bob-supply supply which was previously not
documented.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220426105501.73200-4-krzysztof.kozlowski@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>