hal: passthough not working for IEC61937 HBR content

-For IEC61937 passthough, channel count is alwasy two.
-Channel cound should be eight for HBR content.
-Fix is done to read the channel count from the stream info.

Change-Id: Icb949a7a65031be7477c9c77974c0bdb47bdbd3f
diff --git a/hal/audio_extn/passthru.c b/hal/audio_extn/passthru.c
index 99949fc..8782873 100755
--- a/hal/audio_extn/passthru.c
+++ b/hal/audio_extn/passthru.c
@@ -207,6 +207,8 @@
        channel_count = audio_channel_count_from_out_mask(out->channel_mask);
 #endif
        break;
+    case AUDIO_FORMAT_IEC61937:
+       channel_count = audio_channel_count_from_out_mask(out->channel_mask);
    default:
        break;
    }