nvmem: add binding for mxs-ocotp

This patch adds the devicetree bindings for the Freescale MXS On Chip
OTP driver.
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/nvmem/mxs-ocotp.txt

+On-Chip OTP Memory for Freescale i.MX23/i.MX28
+
+Required properties :
+- compatible :
+  - "fsl,imx23-ocotp" for i.MX23
+  - "fsl,imx28-ocotp" for i.MX28
+- #address-cells : Should be 1
+- #size-cells : Should be 1
+- reg : Address and length of OTP controller registers
+- clocks : Should contain a reference to the hbus clock
+
+= Data cells =
+Are child nodes of mxs-ocotp, bindings of which as described in
+bindings/nvmem/nvmem.txt
+
+Example for i.MX28:
+
+	ocotp: ocotp@8002c000 {
+		compatible = "fsl,imx28-ocotp", "fsl,ocotp";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		reg = <0x8002c000 0x2000>;
+		clocks = <&clks 25>;
+		status = "okay";
+	};