MEDIUM: stream-int/conn-stream: Handle I/O subscriptions in the conn-stream

MEDIUM: stream-int/conn-stream: Handle I/O subscriptions in the conn-stream

wait_event structure is moved in the conn-stream. The tasklet is only
created if the conn-stream is attached to a mux and released when the mux is
detached. This implies a subtle change. In stream_int_chk_rcv() function,
the wakeup of the tasklet was removed because there is no longer tasklet at
this stage (stream_int_chk_rcv() is a callback function of si_embedded_ops).