Test: Add Secure Client 2 test partition

Adds the Secure Client 2 test partition, which provides a service to
call test functions by ID within the execution context of this
partition.

This makes it possible to test scenarios involving multiple partitions.

Change-Id: I6183fc1d0f9d6f23c01e638ce9589afdb919eb47
Signed-off-by: Jamie Fox <jamie.fox@arm.com>
18 files changed