For yet unknown reason, MCP89 on MBP 7,1 doesn't work w/ ahci under
linux but the controller doesn't require explicit mode setting and
works fine with ata_generic.  Make ahci ignore the controller on MBP
7,1 and let ata_generic take it for now.

Reported in bko#15923.

  https://bugzilla.kernel.org/show_bug.cgi?id=15923

NVIDIA is investigating why ahci mode doesn't work.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Peer Chen <pchen@nvidia.com>
Cc: stable@kernel.org
Reported-by: NAnders Østhus <grapz666@gmail.com>
Reported-by: NAndreas Graf <andreas_graf@csgraf.de>
Reported-by: NBenoit Gschwind <gschwind@gnu-log.net>
Reported-by: NDamien Cassou <damien.cassou@gmail.com>
Reported-by: tixetsal@juno.com
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>