netlink: remove unused 'compare' function

No users in the tree.  Tested with allmodconfig build.
Signed-off-by: Florian Westphal <fw@strlen.de>
Link: https://lore.kernel.org/r/20230308142006.20879-1-fw@strlen.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netlink.h

@@ -50,7 +50,6 @@ struct netlink_kernel_cfg {
 	struct mutex	*cb_mutex;
 	int		(*bind)(struct net *net, int group);
 	void		(*unbind)(struct net *net, int group);
-	bool		(*compare)(struct net *net, struct sock *sk);
 };
 
 struct sock *__netlink_kernel_create(struct net *net, int unit,

net/netlink/af_netlink.c

@@ -2097,8 +2097,6 @@ __netlink_kernel_create(struct net *net, int unit, struct module *module,
 			nl_table[unit].bind = cfg->bind;
 			nl_table[unit].unbind = cfg->unbind;
 			nl_table[unit].flags = cfg->flags;
-			if (cfg->compare)
-				nl_table[unit].compare = cfg->compare;
 		}
 		nl_table[unit].registered = 1;
 	} else {

net/netlink/af_netlink.h

@@ -64,7 +64,6 @@ struct netlink_table {
 	struct module		*module;
 	int			(*bind)(struct net *net, int group);
 	void			(*unbind)(struct net *net, int group);
-	bool			(*compare)(struct net *net, struct sock *sock);
 	int			registered;
 };