ata_piix: fix macbook ich8m problems

ICH8M on macbooks are peculiar in that some of them lock up when the
second port is enabled, some return bogus values on SIDPR access while
yet others hang on SIDPR access.  Also, the ich8m_apple_sata entry was
wrongly added below generic ich8m entry making it virtually useless.

This patch works around macbook ich8m problems by

* moving ich8m_apple_sata entry above generic ich8m entry
* dropping PIIX_FLAG_SIDPR from ich8m_apple_sata
* adding subsystem 106b:00a1 as ich8m_apple_sata

Reported and tested by MATSUBAYASHI.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: MATSUBAYASHI 'Shaolin' Kohji <shaolin@rhythmaning.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>