ARM: imx: Correct ocotp id for serial number support of i.MX6ULL/ULZ SoCs

After the commit 8267ff89 ("ARM: imx: Add serial number support for i.MX6/7 SoCs")
the kernel doesn't start on i.MX6ULL/ULZ SoC.
Tested on next-20191205.

For i.MX6ULL/ULZ the variable "ocotp_compat" is set to "fsl,imx6ul-ocotp", but with commit
ffbc34bf ("nvmem: imx-ocotp: Implement i.MX6ULL/ULZ support") and commit
f243bc82 ("ARM: dts: imx6ull: Fix i.MX6ULL/ULZ ocotp compatible") the value
"fsl,imx6ull-ocotp" is already defined and set in device tree...

By setting "ocotp_compat" to "fsl,imx6ull-ocotp" the kernel does boot.

Fixes: 8267ff89 ("ARM: imx: Add serial number support for i.MX6/7 SoCs")
Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/mach-imx/cpu.c

@@ -148,11 +148,11 @@ struct device * __init imx_soc_device_init(void)
 		soc_id = "i.MX6UL";
 		break;
 	case MXC_CPU_IMX6ULL:
-		ocotp_compat = "fsl,imx6ul-ocotp";
+		ocotp_compat = "fsl,imx6ull-ocotp";
 		soc_id = "i.MX6ULL";
 		break;
 	case MXC_CPU_IMX6ULZ:
-		ocotp_compat = "fsl,imx6ul-ocotp";
+		ocotp_compat = "fsl,imx6ull-ocotp";
 		soc_id = "i.MX6ULZ";
 		break;
 	case MXC_CPU_IMX6SLL: