iio: dac: cio-dac: Fix max DAC write value check for 12-bit

iio: dac: cio-dac: Fix max DAC write value check for 12-bit

commit c3701185ee1973845db088d8b0fc443397ab0eb2 upstream.

The CIO-DAC series of devices only supports DAC values up to 12-bit
rather than 16-bit. Trying to write a 16-bit value results in only the
lower 12 bits affecting the DAC output which is not what the user
expects. Instead, adjust the DAC write value check to reject values
larger than 12-bit so that they fail explicitly as invalid for the user.

Fixes: 9ecdeea135a6 ("iio: Add IIO support for the Measurement Computing CIO-DAC family")
Cc: stable@vger.kernel.org
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/r/20230311002248.8548-1-william.gray@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>