iio: adc: mcp3911: add support for the whole MCP39xx family

Microchip does have many similar chips, add support for those.

The new supported chips are:
  - microchip,mcp3910
  - microchip,mcp3912
  - microchip,mcp3913
  - microchip,mcp3914
  - microchip,mcp3918
  - microchip,mcp3919

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230822192259.1125792-7-marcus.folkesson@gmail.com


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