feat(st): add the TRUSTED_BOARD_BOOT build config

Add the TRUSTED_BOARD_BOOT option for the STM32MP15 and
STM32MP13 boards.
It will includes the specific files to manage authentication
and decryption.
Add two specific STM32MP13 configurations to use ECDSA Brainpool
algorithms.

Signed-off-by: Lionel Debieve <lionel.debieve@foss.st.com>
Change-Id: I25e79b79e8cee067524fece148c4cb3a5c79d7f0
7 files changed