policy_hal: set channel mask from config at getOutputForAttr
In case the channel mask is not set as part of the
offload info, use the channel mask from audio config
so offload capability can be validated.

Change-Id: Icc7eb088f8177414106ae8cf98e82f60b6d755f4
diff --git a/policy_hal/AudioPolicyManager.cpp b/policy_hal/AudioPolicyManager.cpp
index 00625a3..1c5b792 100644
--- a/policy_hal/AudioPolicyManager.cpp
+++ b/policy_hal/AudioPolicyManager.cpp
@@ -1452,6 +1452,8 @@
         } else {
             ALOGI("%s:: attribute is NULL .. no usage set", __func__);
         }
+    } else if (tConfig.offload_info.channel_mask == AUDIO_CHANNEL_NONE) {
+        tConfig.offload_info.channel_mask = config->channel_mask;
     }
 
     return AudioPolicyManager::getOutputForAttr(attr, output, session, stream,