dw-hdmi i2c master controller

- add support for the HDMI I2C master controller, for boards that
  can have their DDC pins connected only to the HDMI TX directly.

* tag 'dw-hdmi-next-2016-09-19' of git://git.pengutronix.de/git/pza/linux:
  drm: bridge/dw_hdmi: add dw hdmi i2c bus adapter support
  drm: dw_hdmi: use of_get_i2c_adapter_by_node interface