piix: add support for ICH7 on Acer 5602aWLMi

In piix.c (and in ata_piix.c) are already included some patches to skip the
cable check on some laptops and to enable UDMA > 33 modes, but I've noticed
than theese doesn't work on my Acer Aspire 5602WLMi (maybe exist more
versions of this laptop).  With this simple patch I can set transfer mode
to UDMA100.

From: "sebdeg@ngi.it" <sebdeg@ngi.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>