NFS: Remove nfs_unique_id

Clean up:  this structure is unused.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4_fs.h

@@ -52,11 +52,6 @@ struct nfs4_minor_version_ops {
 	const struct nfs4_state_maintenance_ops *state_renewal_ops;
 };
 
-struct nfs_unique_id {
-	struct rb_node rb_node;
-	__u64 id;
-};
-
 #define NFS_SEQID_CONFIRMED 1
 struct nfs_seqid_counter {
 	ktime_t create_time;