dt-bindings: clock: Add Apple NCO

The NCO block found on Apple SoCs is a programmable clock generator
performing fractional division of a high frequency input clock.

Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20220208183411.61090-2-povik+lin@cutebit.org


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