net: make struct request_sock_ops::obj_size unsigned

This field is sizeof of corresponding kmem_cache so it can't be negative.

Space will be saved after 32-bit kmem_cache_create() patch.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/request_sock.h

@@ -29,7 +29,7 @@ struct proto;
 
 struct request_sock_ops {
 	int		family;
-	int		obj_size;
+	unsigned int	obj_size;
 	struct kmem_cache	*slab;
 	char		*slab_name;
 	int		(*rtx_syn_ack)(const struct sock *sk,