Build: Disable CORE test for IPC model

Core test is enabled in reference board while regression is set. Disable
core test in this case due to some items are not ready for working under
IPC model and cause test errors (TFM_CORE_TEST_1007 e.g.).

Change-Id: I4fbfead047fe873be9b732fc7253885c234e7685
Signed-off-by: Edison Ai <edison.ai@arm.com>
1 file changed