linux-phytec-ti

i2c: rcar: add compatible entry for r8a7791

While we are here, also brush up the devicetree binding documentation.
The example was an inappropriate copy from the sh_mobile driver.

Signed-off-by: Wolfram Sang <wsa@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>