ppc/mpc8xx: remove ppc_ide_md hooks

ppc/mpc8xx: remove ppc_ide_md hooks

* Initialize IDE ports in mpc8xx_ide_probe().

* Remove m8xx_ide_init() and ppc_ide_md hooks - no need for them
  (IDE mpc8xx host driver takes care of all this setup).

* Remove needless 'if (irq)' and 'if (data_port >= MAX_HWIFS)' checks
  from m8xx_ide_init_hwif_ports().

* Remove 'ctrl_port' and 'irq' arguments from m8xx_ide_init_hwif_ports().

* Rename m8xx_ide_init_hwif_ports() to m8xx_ide_init_ports().

* Add __init tag to m8xx_ide_init_ports().

This patch fixes hwif->irq always being overriden to 0 (== auto-probe, is
this even working on PPC?) because of ide_init_default_irq() call in ide.c.

There should be no other functional changes.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Vitaly Bordug <vitb@kernel.crashing.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>