sound: oss/vwsnd: Always define vwsnd_mutex

While the conversion of BKL to mutex in commit 645ef9ef, the mutex
definition was put in a wrong place inside #ifdef WSND_DEBUG, which
leads to the build error.  Just move it outside the ifdef.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/oss/vwsnd.c

@@ -155,12 +155,13 @@
 
 #include "sound_config.h"
 
+static DEFINE_MUTEX(vwsnd_mutex);
+
 /*****************************************************************************/
 /* debug stuff */
 
 #ifdef VWSND_DEBUG
 
-static DEFINE_MUTEX(vwsnd_mutex);
 static int shut_up = 1;
 
 /*