Build: Support building IPC model without tests

Refactors the build configuration variables so that the Core IPC tests
are only built if either CORE_TEST or REGRESSION is enabled (as well as
CORE_IPC). This matches the build behaviour for library model.

Adds a TFM_PARTITION_TEST_CORE_IPC build variable to make it possible
to compile-out the Core IPC test partition when the Core IPC tests are
not built.

Removes some unneeded build system behaviour that was conditional on
CORE_TEST to avoid causing problems when CORE_IPC is enabled.

Change-Id: Ia88bd3785817cc2dcedf88b737690fc32cc3266e
Signed-off-by: Jamie Fox <jamie.fox@arm.com>
diff --git a/secure_fw/services/tfm_partition_defs.inc b/secure_fw/services/tfm_partition_defs.inc
index 3a0b197..19e459d 100644
--- a/secure_fw/services/tfm_partition_defs.inc
+++ b/secure_fw/services/tfm_partition_defs.inc
@@ -36,13 +36,13 @@
 #define TFM_SP_SECURE_TEST_PARTITION_ID (TFM_SP_BASE + 7)
 #endif /* TFM_PARTITION_TEST_SECURE_SERVICES */
 
-#ifdef TFM_PSA_API
+#ifdef TFM_PARTITION_TEST_CORE_IPC
 #define TFM_SP_IPC_SERVICE_TEST_ID (TFM_SP_BASE + 8)
-#endif /* TFM_PSA_API */
+#endif /* TFM_PARTITION_TEST_CORE_IPC */
 
-#ifdef TFM_PSA_API
+#ifdef TFM_PARTITION_TEST_CORE_IPC
 #define TFM_SP_IPC_CLIENT_TEST_ID (TFM_SP_BASE + 9)
-#endif /* TFM_PSA_API */
+#endif /* TFM_PARTITION_TEST_CORE_IPC */
 
 #define TFM_MAX_USER_PARTITIONS (10)