Bluetooth: Controller: Add explicit LLCP error code check Add unit tests to cover explicit LLCP error code check and cover the same in the Controller implementation. Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no> (cherry picked from commit d6f2bc96690f5c89e1dc5974024e07dae04a9d77) Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>