Expect spci_rx_release() to be successful in tests.

Bug: 146208457
Change-Id: I2f146c92fb64aa7bf2ac54aa2b4f19c386f64280
diff --git a/test/hftest/service.c b/test/hftest/service.c
index 0d35aa1..afbf6f6 100644
--- a/test/hftest/service.c
+++ b/test/hftest/service.c
@@ -105,7 +105,7 @@
 	ASSERT_EQ(ret.func, SPCI_MSG_SEND_32);
 	memiter_init(&args, recv, spci_msg_send_size(ret));
 	service = find_service(&args);
-	spci_rx_release();
+	EXPECT_EQ(spci_rx_release().func, SPCI_SUCCESS_32);
 
 	/* Check the service was found. */
 	if (service == NULL) {