common_audio: Made input signal const in WebRtcSplFilterMAFastQ12()

BUG=3353, 1133
TESTED=locally on Mac and trybots
R=henrik.lundin@webrtc.org, kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/37499004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@8037 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/audio_coding/neteq/expand.cc b/webrtc/modules/audio_coding/neteq/expand.cc
index 49ea45f..d13c2cd 100644
--- a/webrtc/modules/audio_coding/neteq/expand.cc
+++ b/webrtc/modules/audio_coding/neteq/expand.cc
@@ -618,9 +618,11 @@
     memcpy(unvoiced_vector - kUnvoicedLpcOrder,
            &(audio_history[signal_length - 128 - kUnvoicedLpcOrder]),
            sizeof(int16_t) * kUnvoicedLpcOrder);
-    WebRtcSpl_FilterMAFastQ12(
-        const_cast<int16_t*>(&audio_history[signal_length - 128]),
-        unvoiced_vector, parameters.ar_filter, kUnvoicedLpcOrder + 1, 128);
+    WebRtcSpl_FilterMAFastQ12(&audio_history[signal_length - 128],
+                              unvoiced_vector,
+                              parameters.ar_filter,
+                              kUnvoicedLpcOrder + 1,
+                              128);
     int16_t unvoiced_prescale;
     if (WebRtcSpl_MaxAbsValueW16(unvoiced_vector, 128) > 4000) {
       unvoiced_prescale = 4;