ppc/pmac: remove no longer needed IDE quirk

IDE PMAC host driver and all IDE PCI host drivers use pci_enable_device()
nowadays so the following quirk in pmac_pcibios_after_init() can be removed.

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