tc: Update scp_revision to ac2b4f1 for TC3

The SCP BL1 image is a pre-built, signed image for the
tests on the TC platform. Also use the corresponding
pre-built SCP BL2 image in the tests.

Change-Id: Ia85f94ddfd0134179ff170a53794d7b8514556bf
Signed-off-by: David Vincze <david.vincze@arm.com>
3 files changed