DirectSound: don't alloc p_sys if we're gonna fail

If DSOUND.DLL is unavailable, just fail fast.

modules/audio_output/directx.c

@@ -861,18 +861,20 @@ static int DeviceSelect (audio_output_t *aout, const char *id)
 static int Open(vlc_object_t *obj)
 {
     audio_output_t *aout = (audio_output_t *)obj;
-    aout_sys_t *sys = calloc(1, sizeof (*sys));
-    if (unlikely(sys == NULL))
-        return VLC_ENOMEM;
 
-    sys->hdsound_dll = LoadLibrary(_T("DSOUND.DLL"));
-    if (sys->hdsound_dll == NULL)
+    HINSTANCE hdsound_dll = LoadLibrary(_T("DSOUND.DLL"));
+    if (hdsound_dll == NULL)
     {
         msg_Warn(aout, "cannot open DSOUND.DLL");
-        free(sys);
         return VLC_EGENERIC;
     }
 
+    aout_sys_t *sys = calloc(1, sizeof (*sys));
+    if (unlikely(sys == NULL))
+        return VLC_ENOMEM;
+
+    sys->hdsound_dll = hdsound_dll;
+
     aout->sys = sys;
     aout->start = Start;
     aout->stop = Stop;