ide: remove ide_init_default_irq() macro

* Use ide_default_irq() instead of ide_init_default_irq() in
  ide_generic host driver (so the correct IRQ is always set
  regardless of CONFIG_PCI / CONFIG_BLK_DEV_IDEPCI).

* Remove no longer needed ide_init_default_irq() macro.

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