Refactor haptic constant.

Use the constant from IExternalVibratorService.

Bug: 124318236
Test: play audio-haptic coupled file
Change-Id: Ice2ac13d0f6a6a749bb6243230524336144fa5f4
diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 2d80bd8..4033247 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -347,7 +347,7 @@
             return ret;
         }
     }
-    return AudioMixer::HAPTIC_SCALE_NONE;
+    return AudioMixer::HAPTIC_SCALE_MUTE;
 }
 
 /* static */