ARM: dts: rockchip: Add unwedge pinctrl entries for dw_hdmi on rk3288

This adds the "unwedge" pinctrl entries introduced by a recent dw_hdmi
change that can unwedge the dw_hdmi i2c bus in some cases.  It's
expected that any boards using this would add:

  pinctrl-names = "default", "unwedge";
  pinctrl-0 = <&hdmi_ddc>;
  pinctrl-1 = <&hdmi_ddc_unwedge>;

Note that this isn't added by default because some boards may choose
to mux i2c5 for their DDC bus (if that is more tested for them).

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>