mpt3sas: Fix initial Reference tag field for 4K PI drives.

Modified driver code to use scsi_prot_ref_tag() API instead of
scsi_get_lba(), while initializing reference tag field in the CDB.

Signed-off-by: Chaitra P B <chaitra.basappa@broadcom.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>