xserver-xorg: fix CVE-2021-4008

Backport patch to fix CVE-2021-4008 for xserver-xorg.

CVE: CVE-2021-4008

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>