dt-bindings: iio: adc: ti,adc128s052: Add adc08c and adc10c family

The adcxx4s communicates with a host processor via an SPI/Microwire Bus
interface. The device family responds with 12bit data, of which the LSB
bits are 0 for the lower resolution devices. I have been able to test
adc102s051, hence adding just the missing ones in that family.

Lets reuse the binding to support the family of devices with name
ADC<bb><c>S<sss>, where
* bb is the resolution in number of bits (8, 10, 12)
* c is the number of channels (1, 2, 4, 8)
* sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
  and 101 for 1 MSPS)

Complete datasheets are available at TI's website here:
  https://www.ti.com/lit/gpn/adc<bb><c>s<sss>.pdf

Handling of 8, 10 and 12 bits converters are the same, the
unavailable bits are 0 in LSB :)

Inspired-by: drivers/hwmon/adcxx.c

Link: https://lore.kernel.org/linux-iio/20220701042919.18180-2-nm@ti.com/


Signed-off-by: Nishanth Menon <nm@ti.com>