Use audio_channel_mask_t for channel mask

Change-Id: I1c1896da48983aa9f1462a4b471f910498816f60
diff --git a/media/libmedia/IAudioFlinger.cpp b/media/libmedia/IAudioFlinger.cpp
index f5d6fd6..71e7c31 100644
--- a/media/libmedia/IAudioFlinger.cpp
+++ b/media/libmedia/IAudioFlinger.cpp
@@ -135,7 +135,7 @@
                                 audio_io_handle_t input,
                                 uint32_t sampleRate,
                                 audio_format_t format,
-                                uint32_t channelMask,
+                                audio_channel_mask_t channelMask,
                                 int frameCount,
                                 track_flags_t flags,
                                 pid_t tid,