Add the function of updating bootindex about fw_boot_order list
in add_boot_device_path(). We should delete the old one if a
device has existed in 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>