By default, on closed devices you cannot revoke any key. To do so, it is
required to compile a U-Boot which instructs the HAB not to set the sticky
bit which write protects that field in the OCOTP controller.
This patch introduces a Yocto macro which allows to configure U-Boot in
that way.
In the ConnectCore 6, the value of this settings is ignored, because HAB never
sets the sticky bit which write protects that field.
https://jira.digi.com/browse/DUB-665
Signed-off-by: Diaz de Grenu, Jose <Jose.DiazdeGrenu@digi.com>