scsi_dh_alua: Remove stale variables

With commit 83ea0e5e ("scsi_dh_alua: use scsi_vpd_tpg_id()") these
variables became obsolete, but weren't removed.

[mkp: Fixed checkpatch warning]

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>