[PATCH] pmac IDE: don't release empty interfaces

From: Thibaut VARENE <T-Bone@parisc-linux.org>

Cleaning up the hwif without knowing its previous state in pmac.c is a big
and potentially dangerous job, and there seems to be no generic code interface
that would provide either a way to properly release an hwif or to clean it up.

Fixes OOPS for empty PMAC interface and add-on PCI controller.

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