soundtrigger: Use "default" instance name for HAL service

"default" implies using "primary" legacy device module.
This doesn't change anything for binderized mode, because
the server was only registering itself as "sound_trigger.primary",
so it was the only possibility anyways.

Usage of "stub" (debugging) module is still possible
if audioflinger and corresponding services are built with
USE_LEGACY_LOCAL_AUDIO_HAL=true (added makefile check to ensure
that).

Test: "Ok Google" from screen off state on sailfish
Bug: 36570720
Change-Id: I88f1ebd4c1efd0f91e37458746c336a4beef33ae
diff --git a/soundtrigger/2.0/default/SoundTriggerHalImpl.h b/soundtrigger/2.0/default/SoundTriggerHalImpl.h
index 8aa9285..4769590 100644
--- a/soundtrigger/2.0/default/SoundTriggerHalImpl.h
+++ b/soundtrigger/2.0/default/SoundTriggerHalImpl.h
@@ -38,7 +38,7 @@
 
 class SoundTriggerHalImpl : public ISoundTriggerHw {
 public:
-        explicit SoundTriggerHalImpl(const char *moduleName = NULL);
+        SoundTriggerHalImpl();
 
         // Methods from ::android::hardware::soundtrigger::V2_0::ISoundTriggerHw follow.
         Return<void> getProperties(getProperties_cb _hidl_cb)  override;