Thats right, the logic has slightly changed. I thought this does not matter as long as
we make sure that exactly one of both ON_SEND or AFTER_SEND is set.
We can stick with the logic
in serial8250_em485_config() (i.e. always set ON_SEND and delete AFTER_SEND in case
of an invalid setting), but I think this will require more than the four lines that we
have now (especially if we want to avoid the !!).