dt-bindings: ata: pata-common: Add missing additionalProperties on child nodes

The PATA child node schema is missing constraints to prevent unknown
properties. As none of the users of this common binding extend the child
nodes with additional properties, adding "additionalProperties: false"
here is sufficient.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>