dt-bindings: cp110: update documentation since DT de-duplication

CP110 master/slave DT files have been merged in a DT de-duplication work
merged in v4.16. Update the syscon documentation accordingly to match
the current state of the DT nodes.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>