ARM: dts: imx23: Add i2c support

The imx23-olinuxino board has an i2c interface exposed on UEXT connector.
This patch provides the generic devicetree infrastructure for a follow-up
patch to add support to the actual board files.
Tested all three possible pin groups with MOD-LCD1x9 from Olimex.

This patch is based on work by Fadil Berisha with his permission. However
all bugs are mine.

Signed-off-by: Harald Geyer <[e-mail]>
Acked-by: Stefan Wahren <[e-mail]>
Acked-by: Marek Vasut <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx23.dtsi

···
 					fsl,voltage = <MXS_VOLTAGE_HIGH>;
 					fsl,pull-up = <MXS_PULL_ENABLE>;
 				};
+
+				i2c_pins_a: i2c@0 {
+					reg = <0>;
+					fsl,pinmux-ids = <
+						MX23_PAD_I2C_SCL__I2C_SCL
+						MX23_PAD_I2C_SDA__I2C_SDA
+					>;
+					fsl,drive-strength = <MXS_DRIVE_8mA>;
+					fsl,voltage = <MXS_VOLTAGE_HIGH>;
+					fsl,pull-up = <MXS_PULL_ENABLE>;
+				};
+
+				i2c_pins_b: i2c@1 {
+					reg = <1>;
+					fsl,pinmux-ids = <
+						MX23_PAD_LCD_ENABLE__I2C_SCL
+						MX23_PAD_LCD_HSYNC__I2C_SDA
+					>;
+					fsl,drive-strength = <MXS_DRIVE_8mA>;
+					fsl,voltage = <MXS_VOLTAGE_HIGH>;
+					fsl,pull-up = <MXS_PULL_ENABLE>;
+				};
+
+				i2c_pins_c: i2c@2 {
+					reg = <2>;
+					fsl,pinmux-ids = <
+						MX23_PAD_SSP1_DATA1__I2C_SCL
+						MX23_PAD_SSP1_DATA2__I2C_SDA
+					>;
+					fsl,drive-strength = <MXS_DRIVE_8mA>;
+					fsl,voltage = <MXS_VOLTAGE_HIGH>;
+					fsl,pull-up = <MXS_PULL_ENABLE>;
+				};
 			};
 
 			digctl@8001c000 {
···
 				status = "disabled";
 			};
 
-			i2c@80058000 {
+			i2c: i2c@80058000 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+				compatible = "fsl,imx23-i2c";
 				reg = <0x80058000 0x2000>;
+				interrupts = <27>;
+				clock-frequency = <100000>;
 				dmas = <&dma_apbx 3>;
 				dma-names = "rx-tx";
 				status = "disabled";