ASoC: SOF: Declare sof_compress_ops in sof-priv.h

Fix the following sparse error:
sound/soc/sof/compress.c:310:25: error: symbol 'sof_compressed_ops' was not declared. Should it be static?

Do not enable set the pd->compress_ops yet as it is not a valid assumption
that real compress support really works when CONFIG_SND_SOC_SOF_COMPRESS
is set as the HDA Probes support also selects it, but compressed audio
is not supported (yet) on Intel platforms.

Fixes: 6324cf90 ("ASoC: SOF: compr: Add compress ops implementation")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20220224172324.17976-1-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/sof-priv.h

@@ -497,6 +497,11 @@ void snd_sof_complete(struct device *dev);
 
 void snd_sof_new_platform_drv(struct snd_sof_dev *sdev);
 
+/*
+ * Compress support
+ */
+extern struct snd_compress_ops sof_compressed_ops;
+
 /*
  * Firmware loading.
  */