atp870u: Remove scam_on from struct atp_unit

scam_on is used only during probe, no need to keep it later.

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>