hal: reset backend config when close a2dp

Reset backend config when close a2dp to avoid
wrong sample rate is set to BT_SCO during call.

CRs-Fixed: 2187253
Change-Id: I1866b8637326d2daa2638e20c92b464fd385613d
diff --git a/hal/audio_extn/a2dp.c b/hal/audio_extn/a2dp.c
index c484713..6207856 100644
--- a/hal/audio_extn/a2dp.c
+++ b/hal/audio_extn/a2dp.c
@@ -1325,8 +1325,9 @@
          val = atoi(value);
          if (audio_is_a2dp_out_device(val)) {
              ALOGV("Received device dis- connect request");
-             reset_a2dp_enc_config_params();
              close_a2dp_output();
+             reset_a2dp_enc_config_params();
+             a2dp_reset_backend_cfg();
          }
          goto param_handled;
      }