dt-bindings: i2c: Add Maxim MAX735x/MAX736x variants

Update the pca954x bindings to add support for the Maxim MAX735x/MAX736x
chips. The functionality will be provided by the existing pca954x driver.

For chips that are powered off by default add a regulator called vdd-supply.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@kernel.org>