qeth: synchronize configuration interface

Synchronize access to the drivers configuration interface.
Also do not allow configuration changes during online/offline
transition.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 52096c9..fd1f48c 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -1100,6 +1100,7 @@
 	spin_lock_init(&card->lock);
 	spin_lock_init(&card->ip_lock);
 	spin_lock_init(&card->thread_mask_lock);
+	mutex_init(&card->conf_mutex);
 	card->thread_start_mask = 0;
 	card->thread_allowed_mask = 0;
 	card->thread_running_mask = 0;