LU-8969 llite: sanity test_56x read failed: Invalid argument

LU-8969 llite: sanity test_56x read failed: Invalid argument

In generic_file_read_iter() does not check EOF before invoke
direct_IO callback. So we have to check it by ourselves.

Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: Ia30d2a42da81beb6c5217f081c18ce4d93553540
Reviewed-on: https://review.whamcloud.com/24552
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>