In BL2, the DDR can be mapped as secured in MMU, as no other SW
has access to it during its execution.
The TZC400 configuration is also updated to reflect this. When using
OP-TEE, the TZC400 is reconfigured at the end of BL2, to match OP-TEE
mapping. Else, SP_min will be in charge to reconfigure TZC400 to set
DDR non-secure.

Change-Id: Ic5ec614b218f733796feeab1cdc425d28cc7c103
Signed-off-by: Yann Gautier <yann.gautier@st.com>