expat: fix CVE-2022-23990

CVE: CVE-2022-23990

Based on Steve Sakoman's patch for branch dunfell, fix CVE-2022-23990
for expat in branch hardknott.

And correct indent as well.

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