dt-bindings: clock: samsung: Add Exynos990 SoC CMU bindings

Add dt-schema documentation for the Exynos990 SoC CMU.

This clock management unit has a topmost block (CMU_TOP)
that generates top clocks for other blocks. Currently the
only other block implemented is CMU_HSI0, which provides
clocks for the USB part of the SoC.

Also, device-tree binding definitions added for these blocks:
- CMU_TOP
- CMU_HSI0

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Igor Belwon <igor.belwon@mentallysanemainliners.org>
Link: https://lore.kernel.org/r/20241209-exynos990-cmu-v4-1-57f07080f9e4@mentallysanemainliners.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>