staging/lustre: remove unused lustre_update.h header

lustre_update.h containts various server-side structures that are
not really relevant for the client.
Also remove the only user of this file that does not actually need it.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>