test(spm): use ffa_helpers for ivy partition

Allow the ivy partition to use the ffa_helpers functions.

To achieve this we create a common struct for ff-a calls that is
used for both parameters and returns, this aligns with the Hafnium
implementation. We can then use preprocessor macros to pick either
SMC or SVC as the conduit depending on the exception level the SP
is running at.

Change-Id: Ic9525baabcf40d15545b6f6d504cf954373f08f9
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
diff --git a/tftf/tests/misc_tests/test_invalid_access.c b/tftf/tests/misc_tests/test_invalid_access.c
index 8b79caf..14be340 100644
--- a/tftf/tests/misc_tests/test_invalid_access.c
+++ b/tftf/tests/misc_tests/test_invalid_access.c
@@ -301,7 +301,7 @@
 		sizeof(struct ffa_memory_region_constituent);
 	ffa_memory_handle_t handle;
 	struct mailbox_buffers mb;
-	smc_ret_values ret;
+	struct ffa_value ret;
 
 	if (get_armv9_2_feat_rme_support() == 0U) {
 		return TEST_RESULT_SKIPPED;