tf-a-main: add 'tf-plat-tests' tests group

These tests were only part of the level-2 CI. Add them to the daily
job as well to avoid confusion, as they do not add a lot of overhead.

Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Change-Id: I4a601b9be86a8979ce0437463649f83adaebf905
1 file changed