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

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

After the commit b9eeb258a3ce ("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
3e3f25555e42 ("nvmem: imx-ocotp: Implement i.MX6ULL/ULZ support") and commit
40407fa51522 ("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: b9eeb258a3ce ("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>