[PATCH] ahci: add support for VIA VT8251

Adds AHCI support for the VIA VT8251.

Includes a workaround for a hardware bug which requires a Command List
Override before softreset.

Signed-off-by: Bastiaan Jacques <b.jacques@planet.nl>
Signed-off-by: Jeff Garzik <jeff@garzik.org>