Remove unused AudioRecord::channels()

It was declared but never implemented or called.

Change-Id: If5846147fcbd7f6d4187971e2044dd6fd3252b42
diff --git a/include/media/AudioRecord.h b/include/media/AudioRecord.h
index 35a0a18..aea65aa 100644
--- a/include/media/AudioRecord.h
+++ b/include/media/AudioRecord.h
@@ -190,7 +190,6 @@
 
             audio_format_t format() const;
             int         channelCount() const;
-            int         channels() const;
             uint32_t    frameCount() const;
             size_t      frameSize() const;
             audio_source_t inputSource() const;