ide: add struct ide_io_ports (take 3)

* Add struct ide_io_ports and use it instead of `unsigned long io_ports[]`
  in ide_hwif_t.

* Rename io_ports[] in hw_regs_t to io_ports_array[].

* Use un-named union for 'unsigned long io_ports_array[]' and 'struct
  ide_io_ports io_ports' in hw_regs_t.

* Remove IDE_*_OFFSET defines.

v2:
* scc_pata.c build fix from Stephen Rothwell.

v3:
* Fix ctl_adrr typo in Sparc-specific part of ns87415.c.
  (Noticed by Andrew Morton)

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