feat(stm32mp1): add the TRUSTED_BOARD_BOOT support

feat(stm32mp1): add the TRUSTED_BOARD_BOOT support

Add the support of the TRUSTED_BOARD_BOOT to authenticate the loaded
FIP using platform CoT management.
It adds TBB platform definition, redefining the standard image ID in
order to decrease requested size in BL2 binary.
Authentication will use mbedTLS library for parsing certificate
configured with a platform configuration.

Change-Id: I9da66b915c5e9e9293fccfce92bef2434da1e430
Signed-off-by: Nicolas Toromanoff <nicolas.toromanoff@st.com>
Signed-off-by: Lionel Debieve <lionel.debieve@foss.st.com>