staging/lustre: remove obd_ost.h

Move the structures defined in lustre/include/obd_ost.h to the one
file that uses them (lustre/osc/osc_request.c). Remove the unused
function osc_update_enqueue(). Remove the then empty header
lustre/include/obd_ost.h.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>