[SCSI] iscsi_tcp: increase max_sectors

For a while now, the block layer has seperated max sectors
and max hw sectors. Software iscsi has no limit so this patch
increases max hw sectors, so we can support large pass through
commands.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>