hisi_sas: reduce max itct entries

Since v2 hw only supports 2048 itct entries, as opposed to 4096 for v1
hw, set the max itct entries to the lower of the two.

It is not anticipated that any device with v1 will ever require to
connect > 2048 devices.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>