mptcp: Constify mptcp_pm_ops

The only usages of mptcp_pm_ops is to assign its address to the small_ops
field of the genl_family struct, which is a const pointer, and applying
ARRAY_SIZE() on it. Make it const to allow the compiler to put it in
read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/pm_netlink.c

@@ -1054,7 +1054,7 @@ fail:
 	return -EMSGSIZE;
 }
 
-static struct genl_small_ops mptcp_pm_ops[] = {
+static const struct genl_small_ops mptcp_pm_ops[] = {
 	{
 		.cmd    = MPTCP_PM_CMD_ADD_ADDR,
 		.doit   = mptcp_nl_cmd_add_addr,