MEDIUM: stream-int: automatically call si_cs_recv_cb() if the cs has data on wake()

MEDIUM: stream-int: automatically call si_cs_recv_cb() if the cs has data on wake()

If the cs has data pending or shutdown and the input channel is still
waiting for reads, let's simply call the recv() function from the wake()
callback. This will allow the lower layers to simply wake the upper one
up without having to consider the recv() nor anything else.