feat(bl): add plat handler for image loading

In case of load error, platform may need to try another instance, either
from another storage, or from the same storage in case of PSA FWU. On
MTD devices such as NAND, it is required to define backup partitions.
A new function plat_setup_try_img_ops() should be called by platform
code to register handlers (plat_try_images_ops) to manage loading
other images.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Lionel Debieve <lionel.debieve@foss.st.com>
Change-Id: Ideaecaf296c0037a26fb4e6680f33e507111378a
5 files changed