audio: Reduce audio output buffer size

period_size is now 19.95 ms, just low enough to use the fast mixer path.
Leaving period_count as 4 for now, and will do more aggressive tuning later.

Change-Id: I25103f5b7e6b1c8b162b79be4678f49e6771429a
diff --git a/audio/audio_hw.c b/audio/audio_hw.c
index 13e26da..da5aa30 100644
--- a/audio/audio_hw.c
+++ b/audio/audio_hw.c
@@ -44,7 +44,7 @@
 struct pcm_config pcm_config = {
     .channels = 2,
     .rate = 44100,
-    .period_size = 1024,
+    .period_size = 880,
     .period_count = 4,
     .format = PCM_FORMAT_S16_LE,
 };