net/s390 drivers: add missing 'const' attribute

Add missing 'const' attribute to avoid the following compile warnings:

drivers/s390/net/ctcm_main.c: In function 'ctcm_init':
drivers/s390/net/ctcm_main.c:1864: warning: assignment from incompatible pointer type
drivers/s390/net/lcs.c: In function 'lcs_init_module':
drivers/s390/net/lcs.c:2468: warning: assignment from incompatible pointer type
drivers/s390/net/claw.c: In function 'claw_init':
drivers/s390/net/claw.c:3408: warning: assignment from incompatible pointer type

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
index 1d43d23..f6cc46d 100644
--- a/drivers/s390/net/lcs.c
+++ b/drivers/s390/net/lcs.c
@@ -2440,7 +2440,7 @@
 	.attrs = lcs_group_attrs,
 };
 
-static struct attribute_group *lcs_group_attr_groups[] = {
+static const struct attribute_group *lcs_group_attr_groups[] = {
 	&lcs_group_attr_group,
 	NULL,
 };