ARM: mxs: get ocotp base address from device tree

Instead of using the static definitions, get ocotp base address from
device tree with mapping.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/boot/dts/imx28.dtsi b/arch/arm/boot/dts/imx28.dtsi
index 56d84bf..64af238 100644
--- a/arch/arm/boot/dts/imx28.dtsi
+++ b/arch/arm/boot/dts/imx28.dtsi
@@ -677,6 +677,7 @@
 			};
 
 			ocotp@8002c000 {
+				compatible = "fsl,ocotp";
 				reg = <0x8002c000 0x2000>;
 				status = "disabled";
 			};