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 <[e-mail]>
Reviewed-by: Sean Paul <[e-mail]>
Signed-off-by: Heiko Stuebner <[e-mail]>

arch/arm/boot/dts/rk3288.dtsi

···
 				rockchip,pins = <7 RK_PC3 2 &pcfg_pull_none>,
 						<7 RK_PC4 2 &pcfg_pull_none>;
 			};
+
+			hdmi_ddc_unwedge: hdmi-ddc-unwedge {
+				rockchip,pins = <7 RK_PC3 RK_FUNC_GPIO &pcfg_output_low>,
+						<7 RK_PC4 2 &pcfg_pull_none>;
+			};
+		};
+
+		pcfg_output_low: pcfg-output-low {
+			output-low;
 		};
 
 		pcfg_pull_up: pcfg-pull-up {