Test: Refactor and re-enable SST policy tests

Changes:
 - Moves the SST policy tests to the non-secure side.
 - Refactors the policy tests to use the SST NS test thread interface.
 - Makes the policy tests more exhaustive and more granular.
 - Re-enables the policy tests for the regression test build.

Change-Id: I7f4c95ab32b860b2430c5a99e1ffc6442d496b28
Signed-off-by: Jamie Fox <jamie.fox@arm.com>
diff --git a/test/framework/non_secure_suites.c b/test/framework/non_secure_suites.c
index fa1c115..e691bcf 100644
--- a/test/framework/non_secure_suites.c
+++ b/test/framework/non_secure_suites.c
@@ -18,6 +18,7 @@
 #ifdef SERVICES_TEST_NS
     /* Non-secure SST test cases */
     {&register_testsuite_ns_sst_interface, 0, 0, 0},
+    {&register_testsuite_ns_sst_policy, 0, 0, 0},
 
 #ifdef TFM_PARTITION_TEST_SST
     /* Non-secure SST referenced access testsuite */