nvmem: Add i.MX6 OCOTP device tree binding documentation

This patch documents the i.MX6 OCOTP device tree binding.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

+Freescale i.MX6 On-Chip OTP Controller (OCOTP) device tree bindings
+
+This binding represents the on-chip eFuse OTP controller found on
+i.MX6Q/D, i.MX6DL/S, i.MX6SL, and i.MX6SX SoCs.
+
+Required properties:
+- compatible: should be one of
+	"fsl,imx6q-ocotp" (i.MX6Q/D/DL/S),
+	"fsl,imx6sl-ocotp" (i.MX6SL), or
+	"fsl,imx6sx-ocotp" (i.MX6SX), followed by "syscon".
+- reg: Should contain the register base and length.
+- clocks: Should contain a phandle pointing to the gated peripheral clock.
+
+Example:
+
+	ocotp: ocotp@021bc000 {
+		compatible = "fsl,imx6q-ocotp", "syscon";
+		reg = <0x021bc000 0x4000>;
+		clocks = <&clks IMX6QDL_CLK_IIM>;
+	};