devicetree: bindings: nvmem: Add compatible string for imx6ul

Add new compatible string for i.MX6UL SOC.
Signed-off-by: Bai Ping <ping.bai@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
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.
+i.MX6Q/D, i.MX6DL/S, i.MX6SL, i.MX6SX and i.MX6UL 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".
+	"fsl,imx6sx-ocotp" (i.MX6SX),
+	"fsl,imx6ul-ocotp" (i.MX6UL),
+	followed by "syscon".
 - reg: Should contain the register base and length.
 - clocks: Should contain a phandle pointing to the gated peripheral clock.