dt-bindings: firmware: qcom,scm: document MSM8226 clocks

Document the clocks (core, bus and iface) used on MSM8226 SCM.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221122092345.44369-1-krzysztof.kozlowski@linaro.org