pata_sis: Fix oops on boot

A small number of SiS setups require special handling (not many judging
by how long this dumb bug survived). A couple of Fedora 7 devel testers
hit an Oops on pata_sis loading which is caused by terminal confusion
between chipset as 'the chipset we have found' and chipset as 'array
iterator'

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>