IB/iser: Do not reduce max_sectors

The iSER driver reduces max_sectors. For example, if you load the
ib_iser module with max_sectors=1024, you will see that
/sys/class/block/<bdev>/queue/max_hw_sectors_kb is 508. It is an
incorrect value. The expected value is (max_sectors * sector_size) /
1024 = 512.

Reducing of max_sectors can cause performance degradation due to
unnecessary splitting of IO requests.

The number of pages per MR has been fixed here, so there is no longer
any need to reduce max_sectors.

Fixes: 9c674815 ("IB/iser: Fix max_sectors calculation")
Signed-off-by: Sergey Gorenko <sergeygo@mellanox.com>
Reviewed-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Acked-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>