ide: factor out code for tuning devices from ide_probe_port()

* Factor out code for tuning devices from ide_probe_port()
  to ide_port_tune_devices().

* Move ide_port_tune_devices() call from ide_probe_port()
  to ide_device_add_all().

There should be no functionality changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>