This reverts commit 6749985302fe002a9cb5672dab9badb11e4e3c36.
A defect was found in the above commit (the input shaper code calls
note_step_generateion_scan_time() for many steppers, so the
input_shaper class can't be used as the index).
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>