[PATCH] libata: Remove dependence on host_set->dev for SAS

Remove some of the dependence on the host_set struct
in preparation for supporting SAS HBAs. Adds a struct device
pointer to the ata_port struct.

Signed-off-by: Brian King <brking@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>