ipv4: icmp: use this_cpu_read() in icmp_sk()

this_cpu_read(*X) is faster than *this_cpu_ptr(X)
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/icmp.c

@@ -206,7 +206,7 @@ static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
  */
 static struct sock *icmp_sk(struct net *net)
 {
-	return *this_cpu_ptr(net->ipv4.icmp_sk);
+	return this_cpu_read(*net->ipv4.icmp_sk);
 }
 
 /* Called with BH disabled */