pm80xx: add support for ATTO devices during SAS address initiailization

ATTO SAS controllers retrieve the SAS address from the NVRAM in a location
different from non-ATTO PMC Sierra SAS controllers.  This patch makes the
necessary adjustments in order to retrieve the SAS address on these types
of adapters.

Signed-off-by: Benjamin Rood <brood@attotech.com>
Reviewed-by: Jack Wang <jinpu.wang@profitbricks.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>