Hi!
Please apply the attached patch.  It adds support for the x32 architecture.
The patch is trivial -- all that needed to be done is adding x32 to
debian/control.  The patch can be applied directly to the d-i/efi-reader git
repository.

If you want to test, as the patch-set for x32 in d-i involves around twenty
packages, you'll want ready packages from the repository at debian-x32.org.
Complete d-i isos are available at http://debian-x32.org/#debian-installer
while debs/udebs/modified sources at http://ftp.debian-x32.org/debian/