net/smc: always call the POLL_IN part of sk_wake_async

Wake up reading file descriptors for a closing socket as well, otherwise
some socket applications may stall.

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>