i915: Fixed initialization of surface

src/gallium/drivers/i915simple/i915_texture.c

@@ -624,8 +624,8 @@ i915_get_tex_surface(struct pipe_screen *screen,
 
    ps = CALLOC_STRUCT(pipe_surface);//ws->surface_alloc(ws);
    if (ps) {
-      assert(ps->refcount);
-      assert(ps->winsys);
+      ps->refcount = 1;
+      ps->winsys = ws;
       pipe_texture_reference(&ps->texture, pt);
       pipe_buffer_reference(ws, &ps->buffer, tex->buffer);
       ps->format = pt->format;