Convert the Renesas R-Mobile I2C Bus Interface (IIC) Device Tree binding
documentation to json-schema.

Document missing properties.
R-Mobile A1 and SH-Mobile have multiple interrupts.
Update the example to match reality.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NWolfram Sang <wsa@kernel.org>