atp870u: Introduce is880(), is885() and remove dev_id

Introduce chip type inline functions to simplify code, allowing to delete
dev_id from struct atp_unit.
Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/atp870u.h

@@ -39,7 +39,6 @@ struct atp_unit
 	unsigned short active_id[2];
 	unsigned short ultra_map[2];
 	unsigned short async[2];
-	unsigned short dev_id;
 	unsigned char sp[2][16];
 	unsigned char r1f[2][16];		
 	struct scsi_cmnd *quereq[2][qcnt];