ASoC: SOF: Introduce snd_sof_dsp_get_mailbox_offset

This will allow us to export mailbox offset in order to
read the fw_ready message from.

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190807150203.26359-3-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ops.h

@@ -119,6 +119,15 @@ static inline int snd_sof_dsp_get_bar_index(struct snd_sof_dev *sdev, u32 type)
 	return sdev->mmio_bar;
 }
 
+static inline int snd_sof_dsp_get_mailbox_offset(struct snd_sof_dev *sdev)
+{
+	if (sof_ops(sdev)->get_mailbox_offset)
+		return sof_ops(sdev)->get_mailbox_offset(sdev);
+
+	dev_err(sdev->dev, "error: %s not defined\n", __func__);
+	return -ENOTSUPP;
+}
+
 /* power management */
 static inline int snd_sof_dsp_resume(struct snd_sof_dev *sdev)
 {