[PATCH] via82cxxx IDE: Add VT8251 ISA bridge

Some motherboards (such as the Asus P5V800-MX) ship a
PCI_DEVICE_ID_VIA_82C586_1 IDE controller alongside a VT8251 southbridge.

This southbridge is currently unrecognised in the via82cxxx IDE driver,
preventing those users from getting DMA access to disks.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>