tcp_splice_conn_update() calls tcp_splice_epoll_ctl() twice: first ignoring
the return value, then checking it. This serves no purpose. If the first
call succeeds, the second call will do exactly the same thing again, since
nothing has changed in conn. If the first call fails, then
tcp_splice_epoll_ctl() itself will EPOLL_CTL_DEL both fds, meaning when
the second call tries to EPOLL_CTL_MOD them it will necessarily fail.
It appears that this duplication was introduced by accident in an
otherwise unrelated patch.
Fixes: bb708111 ("treewide: Packet abstraction with mandatory boundary checks")
Signed-off-by: David Gibson