88SE9128 can do FBS and sets it in HOST_CAP but forgets to set FBSCP
in PORT_CMD.  Implement AHCI_HFLAG_YES_FBS and apply it to 88SE9128.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>