policy_hal: add stereo channel output for voip_rx flag

Stereo output is started with setting voip_rx flag since
voip_rx profile supports Stereo config.

Change-Id: Ib79102cef1f5e4af4cfa8efb106c3297d6f9f8ed
diff --git a/policy_hal/AudioPolicyManager.cpp b/policy_hal/AudioPolicyManager.cpp
index be678bc..1a3f456 100644
--- a/policy_hal/AudioPolicyManager.cpp
+++ b/policy_hal/AudioPolicyManager.cpp
@@ -1498,7 +1498,7 @@
             if (use_primary_out) {
                 *flags = (audio_output_flags_t)(AUDIO_OUTPUT_FLAG_FAST|AUDIO_OUTPUT_FLAG_PRIMARY);
             }
-        } else if ((config->channel_mask == 1) &&
+        } else if ((config->channel_mask == 1 || config->channel_mask == 3) &&
                    (config->sample_rate == 8000 || config->sample_rate == 16000 ||
                     config->sample_rate == 32000 || config->sample_rate == 48000)) {
             //check if VoIP output is not opened already