Convert the Actions Semi Owl I2C DT binding to a YAML schema for
enabling DT validation.

Additionally, add a new compatible string corresponding to the I2C
controller found in the S500 variant of the Actions Semi Owl SoCs
family.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>