When SECURE_BOOT enabled, use HAB verify
Trusty OS image or check its IVT available.

If not available, bootloader consider the TOS
lost unexpected and wipe all data on disk.
Then enter limited fastboot mode. In this situation
only bootloader and tos is able to flash, gpt won't
be available for external.

Change-Id: I04f037f5bd5a51f53174b5b99b2c3053182a8fcf
Signed-off-by: Haoran.Wang <elven.wang@nxp.com>