hpsa: add discovery polling for PT RAID devices.

hpsa: add discovery polling for PT RAID devices.

There are problems with getting configuration change notification
in pass-through RAID environments.  So, activate flag
h->discovery_polling when one of these devices is detected in
update_scsi_devices.

After discovery_polling is set, execute a report luns from
rescan_controller_worker (every 30 seconds).

If the data from report_luns is different than last
time (binary compare), execute a full rescan via update_scsi_devices.

Reviewed-by: Scott Teel <[email protected]>
Reviewed-by: Justin Lindley <[email protected]>
Reviewed-by: Kevin Barnett <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Matthew R. Ochs <[email protected]>
Signed-off-by: Don Brace <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>