scsi: smartpqi: Validate block layer host tag

Prevent OS crashes when a drive is hot removed during I/O stress test.

The I/O request pointer can be invalid if block layer provides incorrect
multi-queue host tag. This can lead to invalid I/O request pointer
dereference.
Reviewed-by: Scott Benesh <scott.benesh@microchip.com>
Reviewed-by: Scott Teel <scott.teel@microchip.com>
Reviewed-by: Mike McGowen <mike.mcgowen@microchip.com>
Reviewed-by: Kevin Barnett <kevin.barnett@microchip.com>
Signed-off-by: Murthy Bhat <Murthy.Bhat@microchip.com>
Signed-off-by: Don Brace <don.brace@microchip.com>
Link: https://lore.kernel.org/r/20230428153712.297638-7-don.brace@microchip.comSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/smartpqi/smartpqi_init.c

@@ -708,7 +708,8 @@ static inline struct pqi_io_request *pqi_alloc_io_request(struct pqi_ctrl_info *
 		}
 	}
 
-	pqi_reinit_io_request(io_request);
+	if (io_request)
+		pqi_reinit_io_request(io_request);
 
 	return io_request;
 }