scsi: smartpqi: Update device scan operations

Change return type from EINPROGRESS to EBUSY to signal applications to
retry a REGNEWD if the driver cannot process the REGNEWD. Events such as
OFA, suspend, and shutdown return EINPROGRESS if a scan is currently
running. This prevents applications from immediately retrying REGNEWD.

Schedule a new REGNEWD if system low on memory.

Link: https://lore.kernel.org/r/161549382157.25025.16054784597622125373.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>