dt-bindings: clocks: stm32mp25: add access-controllers description

access-controllers is an optional property that allows to refer to
domain access controller.
The RCC driver will be able to check if we are allowed to register
clocks for a peripheral.

Signed-off-by: Gabriel Fernandez <gabriel.fernandez@foss.st.com>
Link: https://lore.kernel.org/r/20240419152723.570159-2-gabriel.fernandez@foss.st.com
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>