hisi_sas: add device and slot alloc hw methods

Add methods to use HW specific versions of functions to allocate slot
and device.  HW specific methods are permitted to workaround device id
vs IPTT collision issue in v2 hw.

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