pnfs-obj: Remove redundant EOF from objlayout_io_state

The EOF calculation was done on .read_pagelist(), cached
in objlayout_io_state->eof, and set in objlayout_read_done()
into nfs_read_data->res.eof.

So set it directly into nfs_read_data->res.eof and avoid
the extra member.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>