net/smc: no delay for free tx buffer wait

When no free transfer buffers are available then a work to call
smc_tx_work() is scheduled. Set the schedule delay to zero, because for
the out-of-buffers condition the work can start immediately and will
block in the called function smc_wr_tx_get_free_slot(), waiting for free
buffers.

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>