kernel.bbclass: Give sanity check function an opt-out variable
Having no opt-out method and adding the task to linux-yocto.inc was
causing issues. For example, linux-yocto-dev would often fail because
it uses AUTOREV with no way to dynamically change the PV.
Add a variable to turn off the sanity check, allowing an easy opt out,
and set the opt-out variable in linux-yocto-dev, fixing the issue with
AUTOREV.
Signed-off-by: California Sullivan <california.l.sullivan@intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
