net/smc: move wake up of close waiter

Move the call to smc_close_wake_tx_prepared() (which wakes up a possibly
waiting close processing that might wait for 'all data sent') to
smc_tx_sndbuf_nonempty() (which is the main function to send data).

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>