avcodec/metasound_data: comment out unused variable

Fixes -Wunused-const-variable from
http://fate.ffmpeg.org/report.cgi?time=20150820031140&slot=arm64-darwin-clang-apple-5.1Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/metasound_data.c

@@ -14946,9 +14946,10 @@ static const uint16_t bark_tab_s16_128[] = {
     2, 2, 2, 3, 3, 5, 7, 12, 25, 67
 };
 
+/* unused
 static const uint16_t bark_tab_s16_64[] = {
     1, 1, 2, 2, 3, 6, 11, 38
-};
+}; */
 
 static const uint16_t bark_tab_l16s_1024[] = {
       9,   9,   8,   9,  10,   9,  10,  10,