NetworkPkg: Fix bug in IpSecImpl.c caused by missing parentheses

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Bruce Cran <bruce@cran.org.uk>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
[lersek@redhat.com: updated patch based on Siyuan's feedback]
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18045 6f19259b-4bc3-4df7-8a09-765794883524