ARM: tegra: colibri_t20: iris: annotate i2c busses

Annotate I2C busses: GEN2_I2C and CAM_I2C (I2C3) being unused and
DDC_CLOCK/DATA on X3 pin 15/16 e.g. used for display EDID.
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra20-colibri-iris.dts

@@ -73,6 +73,11 @@ rtc@68 {
 		};
 	};
 
+	/* GEN2_I2C: unused */
+
+	/* CAM_I2C (I2C3): unused */
+
+	/* DDC_CLOCK/DATA on X3 pin 15/16 (e.g. display EDID) */
 	i2c_ddc: i2c@7000c400 {
 		status = "okay";
 	};