Adjust the DirectSound buffer size to support correctly 6 channels

The buffer size must be a multiple of the number of channels*sample_size or looping will break the channel layout.

Close #8483

modules/audio_output/directx.c

@@ -38,7 +38,7 @@
 
 #include "windows_audio_common.h"
 
-#define DS_BUF_SIZE (4*1024*1024)
+#define DS_BUF_SIZE (6*1024*1024)
 
 /*****************************************************************************
  * aout_sys_t: directx audio output method descriptor