ASoc: msm: Serialize soc dsp trigger commands.

- Fast Device switching during playback is resulting in
backend dai shutdown is being invoked before startup is
processed.
- Fix the issue by protecting the trigger function with
spinlock to serialize trigger start and stop cmds.

CRs-fixed: 348790
Change-Id: Id18c4e535ed47c8307d59ad80073335a67a31e13
Signed-off-by: Jayasena Sangaraboina <jsanga@codeaurora.org>
diff --git a/include/sound/soc.h b/include/sound/soc.h
index 8d52423..f51b006 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -815,6 +815,7 @@
 	struct mutex mutex;
 	struct mutex dapm_mutex;
 	struct mutex dsp_mutex;
+	spinlock_t dsp_spinlock;
 
 	bool instantiated;