NFS: simplify and clean cache library

This is a cleanup patch.
Such helpers like nfs_cache_init() and nfs_cache_destroy() are redundant,
because they are just a wrappers around sunrpc_init_cache_detail() and
sunrpc_destroy_cache_detail() respectively.
So let's remove them completely and move corresponding logic to
nfs_cache_register_net() and nfs_cache_unregister_net() respectively (since
they are called together anyway).

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index d5ce5f4..9cbc98a 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -377,14 +377,12 @@
 	if (IS_ERR(nn->nfs_dns_resolve))
 		return PTR_ERR(nn->nfs_dns_resolve);
 
-	nfs_cache_init(nn->nfs_dns_resolve);
 	err = nfs_cache_register_net(net, nn->nfs_dns_resolve);
 	if (err)
 		goto err_reg;
 	return 0;
 
 err_reg:
-	nfs_cache_destroy(nn->nfs_dns_resolve);
 	cache_destroy_net(nn->nfs_dns_resolve, net);
 	return err;
 }
@@ -392,10 +390,8 @@
 void nfs_dns_resolver_cache_destroy(struct net *net)
 {
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
-	struct cache_detail *cd = nn->nfs_dns_resolve;
 
-	nfs_cache_unregister_net(net, cd);
-	nfs_cache_destroy(cd);
+	nfs_cache_unregister_net(net, nn->nfs_dns_resolve);
 	cache_destroy_net(nn->nfs_dns_resolve, net);
 }