dt-bindings: i2c: npcm: support NPCM845

Add compatible and nuvoton,sys-mgr description for NPCM i2c module.

Signed-off-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>