fallout of cleaning-up libutils includes

Test: run & compile
Bug: n/a
Change-Id: I63585ed5a764b9ce7af2187b79ca0c83e683fd7f
diff --git a/services/soundtrigger/SoundTriggerHalHidl.h b/services/soundtrigger/SoundTriggerHalHidl.h
index 916fcc4..0c68cf1 100644
--- a/services/soundtrigger/SoundTriggerHalHidl.h
+++ b/services/soundtrigger/SoundTriggerHalHidl.h
@@ -17,6 +17,7 @@
 #ifndef ANDROID_HARDWARE_SOUNDTRIGGER_HAL_HIDL_H
 #define ANDROID_HARDWARE_SOUNDTRIGGER_HAL_HIDL_H
 
+#include <stdatomic.h>
 #include <utils/RefBase.h>
 #include <utils/KeyedVector.h>
 #include <utils/Vector.h>