Add new defines and update the firmware configuration file
to use directly that defines. It will allow to directly
reflect BL32 size update during build.

Change-Id: Ieb11c9e0bac155d26fda9d0f3b086c55d5ce4783
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/186539


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: CIBUILD <smet-aci-builds@lists.codex.cro.st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@st.com>