DirectSound: always set the original_channels

Ref #13826

(cherry picked from commit 32db92e713d16c2a98730d126b6adcad87b27698)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/audio_output/directsound.c

@@ -772,6 +772,8 @@ static HRESULT Start( vlc_object_t *obj, aout_stream_sys_t *sys,
         }
     }
 
+    fmt->i_original_channels = fmt->i_physical_channels;
+
     int ret = vlc_clone(&sys->eraser_thread, PlayedDataEraser, (void*) obj,
                         VLC_THREAD_PRIORITY_LOW);
     if( unlikely( ret ) )