dt-bindings: interrupt-controller: Convert imx irqsteer to json-schema

Convert the i.MX IRQSTEER binding to DT schema format using json-schema.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Rob Herring <robh@kernel.org>