dt-bindings: clock: exynos850: Add Exynos850 CMU_AUD

CMU_AUD generates Cortex-A32 clock, bus clock and audio clocks for
BLK_AUD. Add clock indices and binding documentation for CMU_AUD.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220809113323.29965-2-semen.protsenko@linaro.org