Test: Get rid of secure test partitions if S tests are disabled

When secure regression tests are disabled, some secure tests
dedicated partitions are still enabled and built. Those partitions
are unnecessary and increase secure binary size.

Skip building and linking those partitions when TEST_S is not
selected.

Signed-off-by: David Hu <david.hu@arm.com>
Change-Id: Ie73401ae7c6454f8073400c7af15c8411c1dcdff
9 files changed