exynos: libaudio: Allow overriding usb playback duration

Change-Id: Iaa89653c90fde694dfd68620f55a3d2bb600e79f
diff --git a/include/libaudio/audiohal/audio_definition.h b/include/libaudio/audiohal/audio_definition.h
index 69191db..a90e9cc 100644
--- a/include/libaudio/audiohal/audio_definition.h
+++ b/include/libaudio/audiohal/audio_definition.h
@@ -32,7 +32,9 @@
 #define PREDEFINED_LOW_CAPTURE_DURATION     4   // 4ms
 
 // Duration for USB Playback and Capture
+#ifndef PREDEFINED_USB_PLAYBACK_DURATION
 #define PREDEFINED_USB_PLAYBACK_DURATION    20  // 20ms
+#endif
 #define PREDEFINED_USB_CAPTURE_DURATION     10  // 10ms