sata_via: add missing PM hooks

For some reason, sata_via is missing PM hooks.  Add them.  Spotted by
Jeroen Janssen <jeroen.janssen@gmail.com>.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Jeroen Janssen <jeroen.janssen@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>