ide_platform: remove struct hwif_prop

* Remove 'if (hwif != hwif_prop.hwif)' check from plat_ide_remove()
  (pdev->dev.driver_data and hwif_prop.hwif are set at the same time
   in plat_ide_probe() and are identical).

* Use hwif->index for ide_unregister() in plat_ide_remove().

* Use local variables instead of hwif_prop.plat_ide[_alt]_mapbase in
  plat_ide_probe() and remove no longer needed struct hwif_prop.

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