ASoC: SOF: IPC4: Introduce message handling functionality

Merge series from Peter Ujfalusi <peter.ujfalusi@linux.intel.com>:

The series adds the basic IPC4 message handling code, implementing the ipc
callbacks.
Due to the difference between IPC3 and IPC4 messaging we need to introduce new
message container for IPC4, but the SOF internal callbacks and structures can be
kept as they were and leaving it for the IPC specific code to handle the
differences.

The series provides the foundation for both lowe level (sound/soc/sof/intel) and
high level IPC4 implementation (topologies, firmware loading, control handling,
etc).

sound/soc/sof/Makefile

@@ -2,7 +2,8 @@
 
 snd-sof-objs := core.o ops.o loader.o ipc.o pcm.o pm.o debug.o topology.o\
 		control.o trace.o iomem-utils.o sof-audio.o stream-ipc.o\
-		ipc3-topology.o ipc3-control.o ipc3.o ipc3-pcm.o ipc3-loader.o
+		ipc3-topology.o ipc3-control.o ipc3.o ipc3-pcm.o ipc3-loader.o\
+		ipc4.o
 ifneq ($(CONFIG_SND_SOC_SOF_CLIENT),)
 snd-sof-objs += sof-client.o
 endif

sound/soc/sof/sof-priv.h

@@ -350,6 +350,9 @@ struct snd_sof_ipc_msg {
 	size_t reply_size;
 	int reply_error;
 
+	/* notification, firmware initiated messages */
+	void *rx_data;
+
 	wait_queue_head_t waitq;
 	bool ipc_complete;
 };
@@ -765,5 +768,6 @@ static inline int sof_resume_clients(struct snd_sof_dev *sdev)
 
 /* Main ops for IPC implementations */
 extern const struct sof_ipc_ops ipc3_ops;
+extern const struct sof_ipc_ops ipc4_ops;
 
 #endif