NFSv4.2: Clean up: Move nfs4_xdr_enc_*xattr() functions

They should be in the nfs4_xdr_enc_*() section, and not at the bottom of
the file.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>