staging/lustre/osc: remove unused OBD methods

Remove the unused OBD device methods:
    osc_brw()
    osc_cancel()
    osc_cancel_unused()
    osc_change_cbdata()
    osc_enqueue()
    osc_punch()
    osc_sync()
and their supporting functions.

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