dt-bindings: i2c-mtk: Delete bindings

The bindings file list bindings for mt1827 and mt8135 but
these bindings are not supported by the driver. Remove the bindings.
Also do some minor style changes to the compatible documentation

Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Wolfram Sang <wsa@the-dreams.de>