ARM: dts: mxs: add pwm-backlight for imx23-evk and imx28-evk

Add pwm device and pwm-backlight for imx23-evk and imx28-evk.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/boot/dts/imx23-evk.dts b/arch/arm/boot/dts/imx23-evk.dts
index 9eca34f..3974959d 100644
--- a/arch/arm/boot/dts/imx23-evk.dts
+++ b/arch/arm/boot/dts/imx23-evk.dts
@@ -51,6 +51,12 @@
 		};
 
 		apbx@80040000 {
+			pwm: pwm@80064000 {
+				pinctrl-names = "default";
+				pinctrl-0 = <&pwm2_pins_a>;
+				status = "okay";
+			};
+
 			auart0: serial@8006c000 {
 				pinctrl-names = "default";
 				pinctrl-0 = <&auart0_pins_a>;
@@ -76,4 +82,11 @@
 			gpio = <&gpio1 29 0>;
 		};
 	};
+
+	backlight {
+		compatible = "pwm-backlight";
+		pwms = <&pwm 2 5000000>;
+		brightness-levels = <0 4 8 16 32 64 128 255>;
+		default-brightness-level = <6>;
+	};
 };