NFS: Create a return_delegation rpc op

Delegations are a v4 feature, so push return_delegation out of the
generic client by creating a new rpc_op and renaming the old function to
be in the nfs v4 "namespace"

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --cc fs/nfs/delegation.c
Simple merge

diff --cc fs/nfs/delegation.h
Simple merge

diff --cc fs/nfs/dir.c
Simple merge

diff --cc fs/nfs/inode.c
Simple merge

diff --cc fs/nfs/nfs3proc.c
Simple merge

diff --cc fs/nfs/nfs4proc.c
Simple merge

diff --cc fs/nfs/proc.c
Simple merge

diff --cc fs/nfs/unlink.c
Simple merge

diff --cc include/linux/nfs_xdr.h
Simple merge