Test: Add testcase for testing outvec write

Change-Id: I855e6a5ad9b073d89aaf404a03a96f895cd5642f
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>
diff --git a/interface/include/tfm_veneers.h b/interface/include/tfm_veneers.h
index f771bb9..0e0f6db 100644
--- a/interface/include/tfm_veneers.h
+++ b/interface/include/tfm_veneers.h
@@ -67,6 +67,7 @@
 int32_t tfm_spm_core_test_2_slave_service_veneer(struct psa_invec *in_vec, size_t in_len, struct psa_outvec *out_vec, size_t out_len);
 int32_t tfm_spm_core_test_2_sfn_invert_veneer(struct psa_invec *in_vec, size_t in_len, struct psa_outvec *out_vec, size_t out_len);
 int32_t tfm_spm_core_test_2_check_caller_client_id_veneer(struct psa_invec *in_vec, size_t in_len, struct psa_outvec *out_vec, size_t out_len);
+int32_t tfm_spm_core_test_2_get_every_second_byte_veneer(struct psa_invec *in_vec, size_t in_len, struct psa_outvec *out_vec, size_t out_len);
 #endif /* TFM_PARTITION_TEST_CORE */
 
 #ifdef TFM_PARTITION_TEST_SST