There's some piece ifdef'ed code that doesn't serve any practical purpose.
Instead add a little comment telling why that funny way of dispatching
(based on request size) is necessary.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1600>
(cherry picked from commit 7735c4462c)