Drop GRUB for 32-bit (ia32) UEFI

This commit in syslinux:

commit 7d9c9eca562857fed25b4c8ef902e3de968d7631
Author: Ady <ady-sf@hotmail.com>
Date:   Sun Sep 20 15:35:52 2015 -0400

    core/fs/lib/loadconfig.c: Add architecture-specific config name to search

    When multiple architectures are on a single media, all will try to use the
    same config, preventing PATH from pointing to an architecture-specific
    directory.

    Signed-off-by: Gene Cumm <gene.cumm@gmail.com>

… should allow us to install syslinux’ UEFI *.c32 modules to architecture-specific directories, and use the PATH directive (?) in per-architecture syslinux config files to point to these directories.

If all this works fine then we can simplify a bit our UEFI support: drop GRUB, and use syslinux both for 32-bit and 64-bit UEFI :)

Related issues

• Related to #15806

Original created by @intrigeri on 12440 (Redmine)