morello: Reintroduce tf-l3 and scp boot tests

Commit 973e6636b893ebb14c9ef9323fe45e942ec09796 disabled
Platform CI tests for Morello because of a major change
in the boot flow.

Update Morello run/build/model scripts to adhere to the
newly introduced TBBR based boot flow, and re-enable the
boot tests.

Signed-off-by: Anurag Koul <anurag.koul@arm.com>
Change-Id: Ib4646e48395e2a6293e4f8bbcf4b85c1b85e7000
9 files changed