audio: Guard WB_AMR callback

Some devices do not support this; some devices are WiFi only
and obviously do not have it.

Change-Id: I6d245eee447bd87849cbdfd41c0cf73c6af714e6
diff --git a/audio/voice.c b/audio/voice.c
index 8d73fd1..3ac1e01 100644
--- a/audio/voice.c
+++ b/audio/voice.c
@@ -401,17 +401,21 @@
             session->wb_amr = true;
         ALOGV("%s: Forcing voice config: %s", __func__, voice_config);
     } else {
-        /* register callback for wideband AMR setting */
-        ret = ril_set_wb_amr_callback(&session->ril,
-                                      voice_session_wb_amr_callback,
-                                      (void *)adev);
-        if (ret != 0) {
-            ALOGE("%s: Failed to register WB_AMR callback", __func__);
-            free(session);
-            return NULL;
-        }
+        if (RIL_UNSOL_SNDMGR_WB_AMR_REPORT > 0) {
+            /* register callback for wideband AMR setting */
+            ret = ril_set_wb_amr_callback(&session->ril,
+                                          voice_session_wb_amr_callback,
+                                          (void *)adev);
+            if (ret != 0) {
+                ALOGE("%s: Failed to register WB_AMR callback", __func__);
+                free(session);
+                return NULL;
+            }
 
-        ALOGV("%s: Registered WB_AMR callback", __func__);
+            ALOGV("%s: Registered WB_AMR callback", __func__);
+        } else {
+            ALOGV("%s: WB_AMR callback not supported", __func__);
+        }
     }
 
     return session;