stm32mp1: add OP-TEE support

Support booting OP-TEE as BL32 boot stage and secure runtime
service.

OP-TEE executes in internal RAM and uses a secure DDR area to store
the pager pagestore. Memory mapping and TZC are configured accordingly
prior OP-TEE boot. OP-TEE image is expected in OP-TEE v2 format where
a header file describes the effective boot images. This change
post processes header file content to get OP-TEE load addresses
and set OP-TEE boot arguments.

Change-Id: I02ef8b915e4be3e95b27029357d799d70e01cd44
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>