[NETLINK]: Mark netlink policies const

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c
index 764a56a..ab41c18 100644
--- a/net/decnet/dn_dev.c
+++ b/net/decnet/dn_dev.c
@@ -638,7 +638,7 @@
 	return dn_dev;
 }
 
-static struct nla_policy dn_ifa_policy[IFA_MAX+1] __read_mostly = {
+static const struct nla_policy dn_ifa_policy[IFA_MAX+1] = {
 	[IFA_ADDRESS]		= { .type = NLA_U16 },
 	[IFA_LOCAL]		= { .type = NLA_U16 },
 	[IFA_LABEL]		= { .type = NLA_STRING,