whom.c: Don't increment atoi(3)'s return value as it's already true.

whom.c: Don't increment atoi(3)'s return value as it's already true.

atoi(3) has returned non-zero and distsw holds that value.  Only the
truthness of distsw matters.  Don't increment distsw, as if to show it's
been set, because that would turn the true -1 to false 0.  Bug pre-dates
git.