ide: fix ide_port_scan() to do ACPI setup after initializing request queues

This makes ide_port_scan()'s behavior match ide_host_register()'s
one and fixes OOPS in elv_may_queue() during port re-scan.

Reported-and-tested-by: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>