drivers: iio: adc: ltc2497: LTC2499 support

drivers: iio: adc: ltc2497: LTC2499 support

The LTC2499 is a 16-channel (eight differential), 24-bit,
ADC with Easy Drive technology and a 2-wire, I2C interface.

Implement support for the LTC2499 ADC by extending the LTC2497
driver. A new chip_info struct is added to differentiate between
chip types and resolutions when reading data from the device.

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/2499fe.pdf
Signed-off-by: Ciprian Regus <ciprian.regus@analog.com>
Link: https://lore.kernel.org/r/20220916140922.2506248-5-ciprian.regus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>