dt-bindings: clock: lan966x: Add LAN966X Clock Controller

This adds the DT bindings documentation for lan966x SoC
generic clock controller.

Signed-off-by: Kavyasree Kotagiri <kavyasree.kotagiri@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20211103061935.25677-3-kavyasree.kotagiri@microchip.com