staging/lustre: shrink lu_object_header by 8 bytes on x86_64

Locate the loh_flags and loh_ref fields together in lu_object_header
to avoid holes and shrink the structure by 8 bytes.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-on: http://review.whamcloud.com/9185
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3059


Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>