fix the undefined symbol error

libs/audio/targets/snd_null.c

@@ -159,6 +159,16 @@ SND_LocalSound (const char *s)
 {
 }
 
+void
+SND_BlockSound (void)
+{
+}
+
+void
+SND_UnblockSound (void)
+{
+}
+
 plugin_t *
 PluginInfo (void) {
     plugin_info.type = qfp_sound;
@@ -202,13 +212,3 @@ PluginInfo (void) {
 
     return &plugin_info;
 }
-
-void
-SNDDMA_BlockSound (void)
-{
-}
-
-void
-SNDDMA_UnblockSound (void)
-{
-}