dt-bindings: ata: imx-pata: Convert to dtschema

Convert the imx-pata bindings to DT schema.
Add missing fsl,imx31-pata and fsl,imx51-pata compatibles during
conversion, because they are already being used in existing DTS.

Signed-off-by: Animesh Agarwal <animeshagarwal28@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>