Expect spci_rx_release() to be successful in tests.

Bug: 146208457
Change-Id: I2f146c92fb64aa7bf2ac54aa2b4f19c386f64280
diff --git a/test/linux/hftest_socket.c b/test/linux/hftest_socket.c
index 6c9a244..a07e188 100644
--- a/test/linux/hftest_socket.c
+++ b/test/linux/hftest_socket.c
@@ -68,7 +68,7 @@
 	/* Set up the mailbox. */
 	spci_rxtx_map(send_addr, recv_addr);
 
-	spci_rx_release();
+	EXPECT_EQ(spci_rx_release().func, SPCI_SUCCESS_32);
 
 	/* Clean the context. */
 	ctx = hftest_get_context();
@@ -98,7 +98,7 @@
 		spci_vm_id_t dst_id = spci_msg_send_sender(ret);
 		spci_vm_id_t src_id = spci_msg_send_receiver(ret);
 
-		spci_rx_release();
+		EXPECT_EQ(spci_rx_release().func, SPCI_SUCCESS_32);
 		EXPECT_EQ(spci_msg_send(src_id, dst_id, spci_msg_send_size(ret),
 					0)
 				  .func,