pico-imx7d: Add bl33 config

Add default configuration to run u-boot as BL33 in the boot flow case
of ATF(ARM Trusted Firmware) -> OPTEE -> U-boot.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
1 file changed