Add the secure device tree in the reserved memory region.
Use dtb_addr variable instead of hardcoded
value.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Change-Id: I2865186d96987d52c747e6b8b3459727afd5cf90
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/178516


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: Etienne CARRIERE <etienne.carriere@st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@st.com>