test(el3-runtime): check DIT is retained on exception

Add a test to check that the PSTATE bits not set in the
Aarch64.TakeException but set to a default when taking an exception to
EL3 are maintained after an exception and that changes in TSP do not
effect the PSTATE in TFTF and vice versa.

Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
Change-Id: Id4d625c7e9cbb565ac236f844274319cc02c2335
7 files changed