nfs: remove data list from pgio header

Since the ability to split pages into subpage requests has been added,
nfs_pgio_header->rpc_list only ever has one pgio data.

Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

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

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

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