The IPC message representation of an IPC4 differs from the IPC3 version
significantly.

The message for IPC4 should be written to the debugfs file in this form:
0-7 IPC4 header (2x u32)
8-  additional payload, if any

The reply is given back in the same form.

The message size limitation is the same as with the IPC3, only messages
which can fit to the mailbox can be injected (and received).
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20220506132647.18690-8-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>