staging:iio:accel:sca3000 replace non standard revision attr with dev_info on probe

There seems little point in being able to query the part revision number
via sysfs.  Hence just put it in the kernel logs during probe incase
anyone ever wants to know.

Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>