atp870u: Remove chip_ver from struct atp_unit

chip_ver is used for wide chip detection only. Remove it and use a local
variable instead (for 870; 880 and 885 are always wide).

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>