Falcon mode was disabled for TI_SECURE_DEVICE at commit e95b9b4437
("ti_armv7_common: Disable Falcon Mode on HS devices") for older 32-bit
HS devices and but can now be enabled with the addition of
OS_BOOT_SECURE.
For secure boot, the kernel with x509 headers can be packaged in a fit
container (fitImage) signed with TIFS keys for authentication.
Signed-off-by: Anshul Dalal <anshuld@ti.com>