dt-bindings: clocks: stm32mp25: add description of all parents

RCC driver uses '.index' to define all parent clocks instead '.names'
because the use of a name to define a parent clock is discouraged. This
is an ABI change, but the RCC driver has not yet merged, unlike all
others drivers besides Linux.

Fixes: b5be49db ("dt-bindings: stm32: add clocks and reset binding for stm32mp25 platform")
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@foss.st.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240411092453.243633-3-gabriel.fernandez@foss.st.com


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