build(stm32mp1): update STM32MP1 compilation script

The STM32MP1 compilation shouldn't be restricted to only compile the
different bls. This was done because of device tree compiler version.
The pre_tf_build() is then removed, and the DTB_FILE_NAME is added.

Change-Id: I56c1cd12f90bd5a6a481827ede9707d3a7a25b46
Signed-off-by: Yann Gautier <yann.gautier@st.com>
2 files changed