fallout of cleaning-up libutils includes

Test: run & compile
Bug: n/a

Change-Id: I9ad9f3358cceb15d3d8c97d2444fb74ee04bd9f8
diff --git a/soundtrigger/2.0/default/SoundTriggerHalImpl.h b/soundtrigger/2.0/default/SoundTriggerHalImpl.h
index 4e0d01d..8aa9285 100644
--- a/soundtrigger/2.0/default/SoundTriggerHalImpl.h
+++ b/soundtrigger/2.0/default/SoundTriggerHalImpl.h
@@ -20,6 +20,7 @@
 #include <android/hardware/soundtrigger/2.0/ISoundTriggerHw.h>
 #include <android/hardware/soundtrigger/2.0/ISoundTriggerHwCallback.h>
 #include <hidl/Status.h>
+#include <stdatomic.h>
 #include <utils/threads.h>
 #include <utils/KeyedVector.h>
 #include <system/sound_trigger.h>