chore: use tabs for indentation

This patch changes definitions of bl2_mem_params_descs to follow the
TF-A coding style documented at
https://trustedfirmware-a.readthedocs.io/en/latest/process/coding-style.html



Signed-off-by: Jorge Troncoso <jatron@google.com>
Change-Id: I7bd99a50a79499aca0d349e49a3e095e6c5d2f08