[S390] Get rid of a lot of sparse warnings.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/net/qeth_sys.c b/drivers/s390/net/qeth_sys.c
index 5836737..fca523a 100644
--- a/drivers/s390/net/qeth_sys.c
+++ b/drivers/s390/net/qeth_sys.c
@@ -998,7 +998,7 @@
 	.store	= _store,						     \
 };
 
-int
+static int
 qeth_check_layer2(struct qeth_card *card)
 {
 	if (card->options.layer2)