dt-bindings: ingenic: Add support for the JZ4755 CGU

Add documentation for the clock generation unit (CGU)
of the JZ4755 SoC.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Siarhei Volkau <lis8215@gmail.com>
Link: https://lore.kernel.org/r/20221027192024.484320-2-lis8215@gmail.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>