smsgiucv: guarantee single iucv connect in thaw

If another smsgiucv_app device exists, suspend / resume fails with
iucv path list corruption, because the same iucv_path_connect is
called twice.
The patch introduces a flag to save connect status of the smsgiucv
path to make sure iucv_path_connect in smsg_pm_restore_thaw is
called only once.

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