iucv: add work_queue cleanup for suspend

If iucv_work_queue is not empty during kernel freeze, a kernel panic
occurs. This suspend-patch adds flushing of the work queue for
pending connection requests and severing of remaining pending
connections.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>