dt-bindings: input: syna,rmi4: Make "additionalProperties: true" explicit

Make it explicit that the not yet documented child nodes have additional
properties and the child node schema is not complete.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230926144249.4053202-1-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

dt-bindings: input: convert syna,rmi4 to DT schema

Convert the bindings for Synaptics RMI4 bus and devices to DT schema.
Changes during conversion:
1. Add reset-gpios already used in DTS and mentioned by RMI4
specification.
2. Do not require address/size cells, because without functions
(children) they aren't really needed.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230728165054.88678-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Rob Herring <robh@kernel.org>