Update output_dev_desc when deciding to skip the mixer

Author: Pehrsons

src/backend/mod.rs

@@ -3895,7 +3895,9 @@ impl<'ctx> CoreStreamData<'ctx> {
                     &layout,
                     mem::size_of::<AudioChannelLayout>(),
                 );
-                if r != NO_ERR {
+                if r == NO_ERR {
+                    self.output_dev_desc.mChannelsPerFrame = 2;
+                } else {
                     cubeb_log!(
                         "AudioUnitSetProperty/output/kAudioUnitProperty_AudioChannelLayout rv={}",
                         r