This was used for non nvmem-layout ubootenv support. Since that's gone
and it's not even used anyway, remove.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/22367
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>