ARM: imx_v6_v7_defconfig: enable OP-TEE

ARM: imx_v6_v7_defconfig: enable OP-TEE

This patch enables configs for Trusted Execution Environment(TEE) and
Open Portable Trusted Execution Environment(OP-TEE).

With Linux running in Trustzone non-secure world, OP-TEE OS runs in
secure world, linux could use secure services provided by OP-TEE.
With TEE/OP-TEE options selected, use the bindings
in Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.txt
to let the driver probe work.

On i.MX6/7, now the bootflow is U-Boot->OP-TEE->Linux, OP-TEE will
automatically create that node.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>