bootindex: support to set a existent device's bootindex to -1 When set a device's bootindex to -1, we remove it from global fw_boot_order list. Signed-off-by: Gonglei <arei.gonglei@huawei.com> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>