pata_sis: implement laptop list and add ASUS A6K/A6U

In ASUS A6K/A6U hdd is connected to SiS 96x via 40c cable, however it
is short cable and is UDMA66 capable.

tj: fixed if () conditionals
ah: fixed infinite loop

Signed-off-by: Jakub W. Jozwicki <jakub007@go2.pl>
Cc: Andreas Henriksson <andreas@fatal.se>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>