dt-bindings: clock: Document Exynos850 CMU bindings

Provide dt-schema documentation for Exynos850 SoC clock controller.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Link: https://lore.kernel.org/r/20211008154352.19519-5-semen.protsenko@linaro.org


Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>