ide: set hwif->dev in ide_init_port_hw() (take 2)

* Add 'parent' field to hw_regs_t for optional parent device pointer (needed
  by macio PMAC IDE controllers) and set hwif->dev in ide_init_port_hw().

* Update au1xxx-ide.c, sgiioc4.c, pmac.c and setup-pci.c accordingly.

v2:

* Update scc_pata.c.

There should be no functional changes caused by this patch.

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