netlink: add netlink_dump_control structure for netlink_dump_start()

Davem considers that the argument list of this interface is getting
out of control. This patch tries to address this issue following
his proposal:

struct netlink_dump_control c = { .dump = dump, .done = done, ... };

netlink_dump_start(..., &c);

Suggested by David S. Miller.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
index 16f8693..b6ac138 100644
--- a/crypto/crypto_user.c
+++ b/crypto/crypto_user.c
@@ -389,9 +389,13 @@
 	    (nlh->nlmsg_flags & NLM_F_DUMP))) {
 		if (link->dump == NULL)
 			return -EINVAL;
-
-		return netlink_dump_start(crypto_nlsk, skb, nlh,
-					  link->dump, link->done, 0);
+		{
+			struct netlink_dump_control c = {
+				.dump = link->dump,
+				.done = link->done,
+			};
+			return netlink_dump_start(crypto_nlsk, skb, nlh, &c);
+		}
 	}
 
 	err = nlmsg_parse(nlh, crypto_msg_min[type], attrs, CRYPTOCFGA_MAX,