hwmon/ams: Do not print error on systems without apple motion sensor

It is not an error if a system has no ams hardware.  Do not clutter dmesg
in this case.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michael Hanselmann <linux-kernel@hansmi.ch>
Signed-off-by: Jean Delvare <khali@linux-fr.org>