scsi: hisi_sas: set dma mask before allocate DMA memory

The device DMA mask was being set after the bulk of the DMA allocations
in the driver init, so potentially DMA allocates fail.  To resolve,
relocate before allocating the DMA memory when initialising the driver.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>