ide: move ide_init_port_data() and friends to ide-probe.c

* Move IDE_DEFAULT_MAX_FAILURES to <linux/ide.h>.

* Move ide_cfg_mtx, ide_hwif_to_major[], ide_port_init_devices_data(),
  ide_init_port_data(), ide_init_port_hw() and ide_unregister() to
  ide-probe.c from ide.c.

* Make ide_unregister(), ide_init_port_data(), ide_init_port_hw()
  and ide_cfg_mtx static.

While at it:

* Remove stale ide_init_port_data() documentation and ide_lock extern.

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