pata_atiixp: update port enabledness test handling

Port enabledness test fits much better into init_one() instead of
pre_reset().  The reason why these tests are in pre_reset() is purely
historical at this point.  Move it to init_one().  This will help
further changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>