ASoC: SOF: uapi: header: Update sof_abi_hdr doc for IPC4 use

With IPC4 the sof_abit_hdr is only used between user space
(and in topology) and kernel.
The same abi header is used with small differencies like different
magic number and the type field have slightly different name, but
similar function in IPC4 (param_id).

Update the kernel documentation to highlight the differences.

Signed-off-by: Peter Ujfalusi <[e-mail]>
Reviewed-by: Bard Liao <[e-mail]>
Reviewed-by: Pierre-Louis Bossart <[e-mail]>
Reviewed-by: Ranjani Sridharan <[e-mail]>
Reviewed-by: Jaska Uimonen <[e-mail]>
Reviewed-by: Kai Vehmanen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

include/uapi/sound/sof/abi.h

···
 
 /* SOF ABI magic number "SOF\0". */
 #define SOF_ABI_MAGIC		0x00464F53
+/* SOF IPC4 ABI magic number "SOF4". */
+#define SOF_IPC4_ABI_MAGIC	0x34464F53
 
 #endif

include/uapi/sound/sof/header.h

···
 
 /**
  * struct sof_abi_hdr - Header for all non IPC ABI data.
- * @magic: Magic number for validation: 0x00464F53 ('S', 'O', 'F', '\0')
- * @type: Component specific type
+ * @magic: Magic number for validation
+ *	   for IPC3 data: 0x00464F53 ('S', 'O', 'F', '\0')
+ *	   for IPC4 data: 0x34464F53 ('S', 'O', 'F', '4')
+ * @type: module specific parameter
+ *	  for IPC3: Component specific type
+ *	  for IPC4: parameter ID (param_id) of the data
  * @size: The size in bytes of the data, excluding this struct
- * @abi: SOF ABI version
+ * @abi: SOF ABI version. The version is valid in scope of the 'magic', IPC3 and
+ *	 IPC4 ABI version numbers have no relationship.
  * @reserved: Reserved for future use
  * @data: Component data - opaque to core
  *