staging/lustre: Drop unused obdo_from_la() and la_from_obdo()

They are no longer used anywhere.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>