i2c: Prevent log spam on some DVB adapters

Some DVB adapters do not support the special I2C transaction that we
use for probing purposes. There's no point in logging this event, as
there's nothing the user can do and in general there is no actual
problem. So, degrade one of these messages to a debug message, and
move the other one around so that it is only printed on bogus drivers.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Uwe Bugla <uwe.bugla@gmx.de>