Add the stm32mp1 CoT description file. Include the TRUSTED_BOARD_BOOT
entry in the platform device tree file.
Add the missing public root key reference for stm32mp15 and the
encryption key reference for stm32mp13.
Change-Id: I0ae2454979a3df6dd3e4361510317742e8fbc109
Signed-off-by: Lionel Debieve <lionel.debieve@foss.st.com>
