* util/i386/efi/grub-install.in: Don't use empty grub_device.

Reported by: Tito Keitel.

util/i386/efi/grub-install.in

@@ -236,7 +236,7 @@ fi
 # this command is allowed to fail (--target=fs already grants us that the
 # filesystem will be accessible).
 partmap_module=
-for x in `$grub_probe --target=partmap --device ${grub_device} 2> /dev/null`; do
+for x in `$grub_probe --target=partmap --device-map=${device_map} ${grubdir} 2> /dev/null`; do
    partmap_module="$partmap_module part_$x";
 done