Pretty up audioflinger dumpsys

Change-Id: I57e44b4c36b99f7149542bbcf9645521c6152dfa
diff --git a/services/audioflinger/AudioFlinger.h b/services/audioflinger/AudioFlinger.h
index e0d1404..ed250dd 100644
--- a/services/audioflinger/AudioFlinger.h
+++ b/services/audioflinger/AudioFlinger.h
@@ -655,6 +655,8 @@
 
 #undef INCLUDING_FROM_AUDIOFLINGER_H
 
+const char *formatToString(audio_format_t format);
+
 // ----------------------------------------------------------------------------
 
 }; // namespace android