scsi: smartpqi: Fix driver synchronization issues

 - Synchronize OFA and controller offline events. Prevent I/O during the
   above conditions.

 - Cleanup pqi_device_wait_for_pending_io() by checking the
   device->scsi_cmds_outstanding instead of walking the device's list of
   commands.

 - Stop failing all I/O for all devices. This was causing OS to retry them,
   delaying OFA.

 - Clean up cache flush. The controller is checked for offline status in
   lower level functions.

Link: https://lore.kernel.org/r/161549382770.25025.789855864026860170.stgit@brunhilda


Reviewed-by: Scott Benesh <scott.benesh@microchip.com>
Reviewed-by: Mike McGowen <mike.mcgowen@microchip.com>
Reviewed-by: Scott Teel <scott.teel@microchip.com>
Signed-off-by: Kevin Barnett <kevin.barnett@microchip.com>
Signed-off-by: Don Brace <don.brace@microchip.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>