dt-bindings: i2c: Convert imx i2c to json-schema

Convert the i.MX I2C binding to DT schema format using json-schema,
some improvements applied, such as update example based on latest DT
file, add more compatible for existing SoCs, and remove unnecessary
common property "pinctrl".

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Link: https://lore.kernel.org/r/1592279454-32551-2-git-send-email-Anson.Huang@nxp.com


Signed-off-by: Rob Herring <robh@kernel.org>