fix(direct message request): incorrect response for illegal transition

FF-A v1.1 EAC0 spec states that partition manager must return DENIED
as the error code when an illegal transition is attempted by a vCPU.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: Ibb86cc4e688c9f64d83a776dddb4434c741d268f
diff --git a/spm/cactus/cactus_tests/cactus_test_direct_messaging.c b/spm/cactus/cactus_tests/cactus_test_direct_messaging.c
index 93bcba1..540ef01 100644
--- a/spm/cactus/cactus_tests/cactus_test_direct_messaging.c
+++ b/spm/cactus/cactus_tests/cactus_test_direct_messaging.c
@@ -63,7 +63,7 @@
 	 * an FF-A direct message, to the first partition.
 	 */
 	bool is_deadlock_detected = (ffa_func_id(ffa_ret) == FFA_ERROR) &&
-				    (ffa_error_code(ffa_ret) == FFA_ERROR_BUSY);
+				    (ffa_error_code(ffa_ret) == FFA_ERROR_DENIED);
 
 	/*
 	 * Should be true after the deadlock has been detected and after the