Update multichannel audio policy handling

Ensure AUDIO_FORMAT_PCM_FLOAT and AUDIO_FORMAT_PCM_32_BIT
have proper precedence.
Allow more mixer channels than 2.

Change-Id: I02af97dad6218b25cbada4d93077a213314c6725
diff --git a/services/audiopolicy/AudioPolicyManager.h b/services/audiopolicy/AudioPolicyManager.h
index 62b3ce5..13a9cf0 100644
--- a/services/audiopolicy/AudioPolicyManager.h
+++ b/services/audiopolicy/AudioPolicyManager.h
@@ -53,10 +53,7 @@
 #define OFFLOAD_DEFAULT_MIN_DURATION_SECS 60
 
 #define MAX_MIXER_SAMPLING_RATE 48000
-#define MAX_MIXER_CHANNEL_COUNT 2
-// See AudioPort::compareFormats()
-#define WORST_MIXER_FORMAT AUDIO_FORMAT_PCM_16_BIT
-#define BEST_MIXER_FORMAT AUDIO_FORMAT_PCM_24_BIT_PACKED
+#define MAX_MIXER_CHANNEL_COUNT 8
 
 // ----------------------------------------------------------------------------
 // AudioPolicyManager implements audio policy manager behavior common to all platforms.