scsi: hpsa: limit transfer length to 1MB

scsi: hpsa: limit transfer length to 1MB

The hpsa 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 7710967a4bafa086e856613ff26cd941c7c29cbb,
which changed max_sectors_kb to 1280k, but the hardware is able to work
fine with it, so the true fix should be from hpsa 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>