scsi: smartpqi: limit transfer length to 1MB

The smartpqi firmware will bypass the cache for any request larger than
1MB, so we should cap the request size to avoid any performance
degradation in kernels later than v4.3

This degradation is caused from d2be537c3b,
which changed max_sectors_kb to 1280k, but the hardware is able to
work fine with it, so the true fix should be from smartpqi driver.

Signed-off-by: Yadan Fan <ydfan@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Acked-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/smartpqi/smartpqi.h

@@ -690,7 +690,7 @@ struct pqi_config_table_heartbeat {
 
 #define PQI_MAX_OUTSTANDING_REQUESTS		((u32)~0)
 #define PQI_MAX_OUTSTANDING_REQUESTS_KDUMP	32
-#define PQI_MAX_TRANSFER_SIZE			(4 * 1024U * 1024U)
+#define PQI_MAX_TRANSFER_SIZE			(1024U * 1024U)
 #define PQI_MAX_TRANSFER_SIZE_KDUMP		(512 * 1024U)
 
 #define RAID_MAP_MAX_ENTRIES		1024