drm: dw_hdmi: use of_get_i2c_adapter_by_node interface

drm: dw_hdmi: use of_get_i2c_adapter_by_node interface

This change is needed to properly lock I2C bus driver, which serves
DDC.

The change fixes an overflow over zero of I2C bus driver user counter:

  root@imx6q:~# lsmod
  Not tainted
  dw_hdmi_ahb_audio 4082 0 - Live 0xbf02c000
  dw_hdmi_imx 3498 0 - Live 0xbf00d000
  dw_hdmi 16398 2 dw_hdmi_ahb_audio,dw_hdmi_imx, Live 0xbf004000
  i2c_imx 16687 0 - Live 0xbf017000

  root@imx6q:~# rmmod dw_hdmi_imx
  root@imx6q:~# lsmod
  Not tainted
  dw_hdmi_ahb_audio 4082 0 - Live 0xbf02c000
  dw_hdmi 16398 1 dw_hdmi_ahb_audio, Live 0xbf004000
  i2c_imx 16687 -1 - Live 0xbf017000
                ^^

  root@imx6q:~# rmmod i2c_imx
  rmmod: ERROR: Module i2c_imx is in use

Note that prior to this change put_device() coupled with
of_find_i2c_adapter_by_node() was missing on error path of
dw_hdmi_bind(), added i2c_put_adapter() there along with the change.

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>