iio: adc: mcp3911: use correct id bits

The device ID should be shifted 6 bits to left according to datasheet.

Fixes: 3a89b289 ("iio: adc: add support for mcp3911")
Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Link: https://lore.kernel.org/r/20221010194641.676484-1-marcus.folkesson@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>