ipv4: clean up cast warning in do_ip_getsockopt

Sparse warns because of implicit pointer cast.

v2: subject line correction, space between "void" and "*"
Signed-off-by: Karoly Kemeny <karoly.kemeny@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_sockglue.c

@@ -1319,7 +1319,7 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
 		if (sk->sk_type != SOCK_STREAM)
 			return -ENOPROTOOPT;
 
-		msg.msg_control = optval;
+		msg.msg_control = (__force void *) optval;
 		msg.msg_controllen = len;
 		msg.msg_flags = flags;