Refactor audio_processing: Free functions return void

There is no point in returning an error when Free() fails. In fact it can only happen if we have a null pointer as object. There is further no place where the return value is used.

Affected components are
- aec
- aecm
- agc
- ns

BUG=441
R=kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/50579004

Cr-Commit-Position: refs/heads/master@{#8966}
diff --git a/webrtc/modules/audio_processing/ns/include/noise_suppression.h b/webrtc/modules/audio_processing/ns/include/noise_suppression.h
index d912f71..14e686a 100644
--- a/webrtc/modules/audio_processing/ns/include/noise_suppression.h
+++ b/webrtc/modules/audio_processing/ns/include/noise_suppression.h
@@ -41,12 +41,8 @@
  *
  * Input:
  *      - NS_inst       : Pointer to NS instance that should be freed
- *
- * Return value         :  0 - Ok
- *                        -1 - Error
  */
-int WebRtcNs_Free(NsHandle* NS_inst);
-
+void WebRtcNs_Free(NsHandle* NS_inst);
 
 /*
  * This function initializes a NS instance and has to be called before any other
diff --git a/webrtc/modules/audio_processing/ns/include/noise_suppression_x.h b/webrtc/modules/audio_processing/ns/include/noise_suppression_x.h
index e1671a6..736cb23 100644
--- a/webrtc/modules/audio_processing/ns/include/noise_suppression_x.h
+++ b/webrtc/modules/audio_processing/ns/include/noise_suppression_x.h
@@ -41,12 +41,8 @@
  *
  * Input:
  *      - nsxInst       : Pointer to NS instance that should be freed
- *
- * Return value         :  0 - Ok
- *                        -1 - Error
  */
-int WebRtcNsx_Free(NsxHandle* nsxInst);
-
+void WebRtcNsx_Free(NsxHandle* nsxInst);
 
 /*
  * This function initializes a NS instance
diff --git a/webrtc/modules/audio_processing/ns/noise_suppression.c b/webrtc/modules/audio_processing/ns/noise_suppression.c
index bae0f2e..0efbebc 100644
--- a/webrtc/modules/audio_processing/ns/noise_suppression.c
+++ b/webrtc/modules/audio_processing/ns/noise_suppression.c
@@ -28,12 +28,10 @@
 
 }
 
-int WebRtcNs_Free(NsHandle* NS_inst) {
+void WebRtcNs_Free(NsHandle* NS_inst) {
   free(NS_inst);
-  return 0;
 }
 
-
 int WebRtcNs_Init(NsHandle* NS_inst, uint32_t fs) {
   return WebRtcNs_InitCore((NoiseSuppressionC*)NS_inst, fs);
 }
diff --git a/webrtc/modules/audio_processing/ns/noise_suppression_x.c b/webrtc/modules/audio_processing/ns/noise_suppression_x.c
index 920b501..a3b6d0f 100644
--- a/webrtc/modules/audio_processing/ns/noise_suppression_x.c
+++ b/webrtc/modules/audio_processing/ns/noise_suppression_x.c
@@ -31,10 +31,9 @@
 
 }
 
-int WebRtcNsx_Free(NsxHandle* nsxInst) {
+void WebRtcNsx_Free(NsxHandle* nsxInst) {
   WebRtcSpl_FreeRealFFT(((NoiseSuppressionFixedC*)nsxInst)->real_fft);
   free(nsxInst);
-  return 0;
 }
 
 int WebRtcNsx_Init(NsxHandle* nsxInst, uint32_t fs) {