ASoC: SOF: sof-priv: Mark fw_tracing ops optional in documentation

The code treats the fw_tracing as optional feature but the documentation
was not reflecting this.
Correct it by explicitly stating that the fw_tracing is optional.
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>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Link: https://lore.kernel.org/r/20221221102328.9635-10-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/sof-priv.h

@@ -444,7 +444,7 @@ struct sof_ipc_pcm_ops;
  * @pm:		Pointer to PM ops
  * @pcm:	Pointer to PCM ops
  * @fw_loader:	Pointer to Firmware Loader ops
- * @fw_tracing:	Pointer to Firmware tracing ops
+ * @fw_tracing:	Optional pointer to Firmware tracing ops
  *
  * @init:	Optional pointer for IPC related initialization
  * @exit:	Optional pointer for IPC related cleanup