code cleanup: rm _e array from icb code
Development description
As decided in March during the Merge fiesta code cleanup session (&11): With nn_hls=2 the default and nn_hls=1 not working anymore, array with extra haloes _e in the icb code are useless and need to be cleaned
Code implementation
- Remove _e array definition and usage
- Remove icb specific lbclnk
Documentation updates
- no update of the documentation needed.