NFS: Create a common nfs_pgio_result_common function

Combining these functions will let me make a single nfs_rw_common_ops
struct (see the next patch).

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

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

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

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

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

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

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