LU-10560 llite: remove assigning f_version in ll_readir.

LU-10560 llite: remove assigning f_version in ll_readir.

Backport upstream patch:
 commit: 8ec426c7019ed9600d9dc0cf758445adcdbfc14e
         lustre: don't set f_version in ll_readdir

Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: I296ce2cf8a7f4f91cf051f281206a7af60b7fb38
Reviewed-on: https://review.whamcloud.com/32268
Tested-by: Jenkins
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>