efi_loader: Fix typo in distro script

The distro script is supposed to use the internal fdt as fallback if we
find no viable other option. However, we're missing a space key to actually
make that work.

Add the space, so we can successfully load an EFI blob even when there is
no device tree provided on the target device.

Signed-off-by: Alexander Graf <agraf@suse.de>