ASoC: dpcm: Explicitly set BE DAI link supported stream directions

Some BE DAIs can be "dummy" (when the DSP is controlling the DAI) and as such
wont have set a minimum number of playback or capture channels required for BE
DAI registration (to establish supported stream directions).

Force machine drivers to explicitly set whether they support playback and capture
stream directions for every BE DAIs.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/include/sound/soc.h b/include/sound/soc.h
index 1f741cb..a5ef14f 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -886,6 +886,10 @@
 	/* This DAI link can route to other DAI links at runtime (Frontend)*/
 	unsigned int dynamic:1;
 
+	/* DPCM capture and Playback support */
+	unsigned int dpcm_capture:1;
+	unsigned int dpcm_playback:1;
+
 	/* pmdown_time is ignored at stop */
 	unsigned int ignore_pmdown_time:1;