netfilter: remove obsolete need_conntrack stub

as of a0ae2562c6c4b27 ("netfilter: conntrack: remove l3proto
abstraction") there are no users anymore.

Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/linux/netfilter/nf_conntrack_common.h

···
 	unsigned int search_restart;
 };
 
-/* call to create an explicit dependency on nf_conntrack. */
-void need_conntrack(void);
-
 #endif /* _NF_CONNTRACK_COMMON_H */

net/netfilter/nf_conntrack_standalone.c

···
 
 module_init(nf_conntrack_standalone_init);
 module_exit(nf_conntrack_standalone_fini);
-
-/* Some modules need us, but don't depend directly on any symbol.
-   They should call this. */
-void need_conntrack(void)
-{
-}
-EXPORT_SYMBOL_GPL(need_conntrack);