build-*: update tftf refernces to tf-a-tests

To maintain consistency with the upstream tf-a test repository [1], the
script file names and references to tftf within the scripts and
configuration files have been modified to tf-a-tests

[1]: https://git.trustedfirmware.org/TF-A/tf-a-tests.git



Signed-off-by: Tony Nadackal <tony.nadackal@arm.com>
Change-Id: I5fe7e739f22f0a35241066f92d24977151d9047d