This reverts commit 37784c48e93c663dafc99454c24bebf4e258556f as the
preference is to have single explicit key for each release/branch.
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Link: https://github.com/openwrt/openwrt/pull/16852
Signed-off-by: Robert Marko <robimarko@gmail.com>