ASoC: topology: ABI - Add sig_bits to stream caps

Kernel struct snd_soc_pcm_stream, SoC PCM stream information, needs this
field. Although current topology users don't configure this, we define it
for future extension.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-topology.c

@@ -1556,6 +1556,7 @@ static void set_stream_info(struct snd_soc_pcm_stream *stream,
 	stream->rate_min = caps->rate_min;
 	stream->rate_max = caps->rate_max;
 	stream->formats = caps->formats;
+	stream->sig_bits = caps->sig_bits;
 }
 
 static void set_dai_flags(struct snd_soc_dai_driver *dai_drv,