Add hlist_bl_add_before/behind helpers to add an element before/after an
existing element in a bl_list.
Co-developed-by: NIlias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: NNikos Tsironis <ntsironis@arrikto.com>
Reviewed-by: NPaul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>