dbe: fix byte swapping in SProcDbeSwapBuffers()

The loop forgot to move the SwapInfo pointer, so the same list entry
gets swapped over and over again, while the remaining ones get ignored.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1822>
(cherry picked from commit 86244ff36f)

dbe/dbe.c

@@ -905,7 +905,7 @@ SProcDbeSwapBuffers(ClientPtr client)
          * followed by a 1 byte swap action and then 3 pad bytes.  We only need
          * to swap the window information.
          */
-        for (i = 0; i < stuff->n; i++) {
+        for (i = 0; i < stuff->n; i++, pSwapInfo++) {
             swapl(&pSwapInfo->window);
         }
     }