qeth: Clear mac_bits field when switching between Layer 2 and Layer 3

This patch fixes a problem that occurs when switching from layer 3 to layer 2
mode. Resetting this mac_bits makes sure that we retrieve our mac address from
the card, otherwise the interface simply would'nt work.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
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_sys.c b/drivers/s390/net/qeth_core_sys.c
index 2eb022f..6b7fd88 100644
--- a/drivers/s390/net/qeth_core_sys.c
+++ b/drivers/s390/net/qeth_core_sys.c
@@ -433,6 +433,7 @@
 	if (card->options.layer2 == newdis)
 		goto out;
 	else {
+		card->info.mac_bits  = 0;
 		if (card->discipline.ccwgdriver) {
 			card->discipline.ccwgdriver->remove(card->gdev);
 			qeth_core_free_discipline(card);