ide: workaround for bogus gcc warning in ide_sysfs_register_port()

Reported-by: "Steven Noonan" <steven@uplinklabs.net>
Suggested-by: "Elias Oltmanns" <eo@nebensachen.de>
Cc: mingo@elte.hu
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>