ipv4: rcu cleanup in ip_ra_control()

Remove one sparse warning :
net/ipv4/ip_sockglue.c:328:22: warning: incorrect type in assignment (different address spaces)
net/ipv4/ip_sockglue.c:328:22:    expected struct ip_ra_chain [noderef] <asn:4>*next
net/ipv4/ip_sockglue.c:328:22:    got struct ip_ra_chain *[assigned] ra

And replace one rcu_assign_ptr() by RCU_INIT_POINTER() where applicable.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_sockglue.c

@@ -303,7 +303,7 @@ int ip_ra_control(struct sock *sk, unsigned char on,
 			}
 			/* dont let ip_call_ra_chain() use sk again */
 			ra->sk = NULL;
-			rcu_assign_pointer(*rap, ra->next);
+			RCU_INIT_POINTER(*rap, ra->next);
 			spin_unlock_bh(&ip_ra_lock);
 
 			if (ra->destructor)
@@ -325,7 +325,7 @@ int ip_ra_control(struct sock *sk, unsigned char on,
 	new_ra->sk = sk;
 	new_ra->destructor = destructor;
 
-	new_ra->next = ra;
+	RCU_INIT_POINTER(new_ra->next, ra);
 	rcu_assign_pointer(*rap, new_ra);
 	sock_hold(sk);
 	spin_unlock_bh(&ip_ra_lock);