afs: Remove set but not used variable 'ret'

Fixes gcc '-Wunused-but-set-variable' warning:

fs/afs/server.c: In function afs_install_server:
fs/afs/server.c:157:6: warning: variable ret set but not used [-Wunused-but-set-variable]

It is not used since commit d2ddc776 ("afs:
Overhaul volume and server record caching and fileserver rotation")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/server.c

@@ -151,7 +151,7 @@ static struct afs_server *afs_install_server(struct afs_net *net,
 	const struct afs_addr_list *alist;
 	struct afs_server *server;
 	struct rb_node **pp, *p;
-	int ret = -EEXIST, diff;
+	int diff;
 
 	_enter("%p", candidate);
 
@@ -196,7 +196,6 @@ static struct afs_server *afs_install_server(struct afs_net *net,
 		hlist_add_head_rcu(&server->addr6_link, &net->fs_addresses6);
 
 	write_sequnlock(&net->fs_addr_lock);
-	ret = 0;
 
 exists:
 	afs_get_server(server, afs_server_trace_get_install);