dt-bindings: cp110: do not depend anymore of the *-clock-output-names

This patch updates the documentation according to the change made in the
patch "clk: mvebu: cp110: do not depend anymore of the
*-clock-output-names": the clock names are no more part of the binding.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>