[NET_SCHED]: Constify struct tcf_ext_map

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
index 436a6e7..b0f90e5 100644
--- a/net/sched/cls_fw.c
+++ b/net/sched/cls_fw.c
@@ -47,7 +47,7 @@
 	struct tcf_exts		exts;
 };
 
-static struct tcf_ext_map fw_ext_map = {
+static const struct tcf_ext_map fw_ext_map = {
 	.action = TCA_FW_ACT,
 	.police = TCA_FW_POLICE
 };