codec/avcodec/vaapi.c: reset surface refcount

Force refcount to one in vlc_va_Get().

modules/codec/avcodec/vaapi.c

@@ -482,7 +482,7 @@ static int Get( vlc_va_t *p_external, AVFrame *p_ff )
     /* NOTE: when the surface is in use and not consumed by vout vaapi-x11,
      * then p_surface->i_refcount can be greater then 0. Thus always increment.
      */
-    p_surface->i_refcount++;
+    p_surface->i_refcount = 1;
     p_surface->i_order = p_va->i_surface_order++;
 
     /* */