ASoC: SOF: ipc4: Add define for the outbox window index

Instead of using the index number directly, add a define for the outbox
window index.
It is always window 1 with IPC4.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20220909114332.31393-4-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc4-priv.h

@@ -13,6 +13,9 @@
 #include <sound/sof/ext_manifest4.h>
 #include "sof-priv.h"
 
+/* The DSP window indices are fixed */
+#define SOF_IPC4_OUTBOX_WINDOW_IDX	1
+
 /**
  * struct sof_ipc4_fw_data - IPC4-specific data
  * @manifest_fw_hdr_offset: FW header offset in the manifest

sound/soc/sof/ipc4.c

@@ -537,7 +537,7 @@ static int ipc4_fw_ready(struct snd_sof_dev *sdev, struct sof_ipc4_msg *ipc4_msg
 		return inbox_offset;
 	}
 	inbox_size = SOF_IPC4_MSG_MAX_SIZE;
-	outbox_offset = snd_sof_dsp_get_window_offset(sdev, 1);
+	outbox_offset = snd_sof_dsp_get_window_offset(sdev, SOF_IPC4_OUTBOX_WINDOW_IDX);
 	outbox_size = SOF_IPC4_MSG_MAX_SIZE;
 
 	sdev->dsp_box.offset = inbox_offset;