staging/lustre: fix coccinelle warnings

drivers/staging/lustre/lustre/llite/dir.c:1416:2-8: Replace memcpy with struct assignment

Generated by: coccinelle/misc/memcpy-assign.cocci

CC: Peng Tao <bergwolf@gmail.com>
CC: Andreas Dilger <andreas.dilger@intel.com>
CC: Oleg Drokin <oleg.drokin@intel.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>