configs: Add configs for j721s2 High Security EVM

Add j721s2 High Security EVM defconfig.

These configs are same as for the non-secure part, except for:
        CONFIG_TI_SECURE_DEVICE option set to 'y'
        CONFIG_FIT_IMAGE_POST_PROCESS option set to 'y'
        CONFIG_SPL_FIT_IMAGE_POST_PROCESS option set to 'y'
        CONFIG_BOOTCOMMAND uses FIT images for booting

Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>