hal: update EC reference handling

Change-Id: I745e28c14902f810754887f9db195cf4f5261713
diff --git a/hal/msm8960/platform.c b/hal/msm8960/platform.c
index 1a8d0ab..bc38b1d 100644
--- a/hal/msm8960/platform.c
+++ b/hal/msm8960/platform.c
@@ -1002,3 +1002,8 @@
 {
     return -ENOSYS;
 }
+
+void platform_set_echo_reference(struct audio_device *adev, bool enable, audio_devices_t out_device)
+{
+    return;
+}