chore: bump SCP version to v2.16

As part of pre-release work for TF-A 2.13, bump the version used in CI
for SCP to the latest available.

Change-Id: I146b5db1628c12007e7eb8907a2cebf07f4744b8
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
1 file changed