fix(ff-a): tests for FFA_FEATURES

There are different expectations to the result to the FFA_FEATURES
call, provided the feature IDs for ME, SRI and NPI interrupt from
tftf or cactus.

This patch refactors the test to keep the common part equal.
For the differences, locally define the expected test target
for the FFA_FEATURES call.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I96f18487c80d789cf4e10ceee0591786708bce51
diff --git a/include/runtime_services/spm_common.h b/include/runtime_services/spm_common.h
index fb1f61e..6c01751 100644
--- a/include/runtime_services/spm_common.h
+++ b/include/runtime_services/spm_common.h
@@ -101,7 +101,10 @@
 
 bool check_spmc_execution_level(void);
 
-unsigned int get_ffa_feature_test_target(const struct ffa_features_test **test_target);
+unsigned int get_ffa_feature_test_target(
+		const struct ffa_features_test **test_target);
+bool ffa_features_test_targets(const struct ffa_features_test *targets,
+			       uint32_t test_target_size);
 
 /**
  * Helper to conduct a memory retrieve. This is to be called by the receiver