NFS store nfs4_deviceid in struct nfs4_filelayout_segment

In preparation for moving the filelayout getdeviceinfo call from
filelayout_alloc_lseg called by pnfs_process_layout

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>