present/wnmd: Free flip_queue entries in present_wnmd_clear_window_flip

When present_wnmd_clear_window_flip is done, present_destroy_window
frees struct present_window_priv, and the events in the flip queue
become unreachable. So if we don't free them first, they're leaked.

Also drop the call to present_wnmd_set_abort_flip, which just sets a
flag in struct present_window_priv and thus can't have any observable
effect after present_destroy_window.

Closes: #1042Reviewed-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit 1bdedc8d)

present/present_screen.c

@@ -115,9 +115,9 @@ present_wnmd_clear_window_flip(WindowPtr window)
     present_window_priv_ptr     window_priv = present_window_priv(window);
     present_vblank_ptr          vblank, tmp;
 
-    if (window_priv->flip_pending) {
-        present_wnmd_set_abort_flip(window);
-        window_priv->flip_pending->window = NULL;
+    xorg_list_for_each_entry_safe(vblank, tmp, &window_priv->flip_queue, event_queue) {
+        present_pixmap_idle(vblank->pixmap, vblank->window, vblank->serial, vblank->idle_fence);
+        present_vblank_destroy(vblank);
     }
 
     xorg_list_for_each_entry_safe(vblank, tmp, &window_priv->idle_queue, event_queue) {