Cactus: FFA Version Test

Added simple test of the FFA interface to cactus:
- FFA version ABI helper;
- New test file for test to FFA ABIs;
- Invoking "ffa_tests" from cactus main.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I8c8445ad6d9da79f1880d143836e7a6da68eaff7
diff --git a/spm/cactus/ffa_helpers.h b/spm/cactus/ffa_helpers.h
index 8f6beb4..8fdf727 100644
--- a/spm/cactus/ffa_helpers.h
+++ b/spm/cactus/ffa_helpers.h
@@ -105,4 +105,15 @@
 	return tftf_smc(&args);
 }
 
+/* FFA Version ABI helper */
+static inline smc_ret_values ffa_version(uint32_t input_version)
+{
+	smc_args args = {
+		.fid = FFA_VERSION,
+		.arg1 = input_version
+	};
+
+	return tftf_smc(&args);
+}
+
 #endif /* __FFA_HELPERS_H__ */