staging: lustre: llite: kzalloc/copy_to_user to memdup_user

kzalloc call followed by copy_to_user can be replaced by call to memdup_user.

Signed-off-by: Tobin C Harding <me@tobin.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>