sensor: convert ADC `depends on` to `select`

When a sensor that depends on an ADC is enabled in devicetree, enable
the ADC subsystem. ADC is roughly equivalent to a bus for these sensors
(the mechanism through which data is transferred), which had the same
conversion applied in #48707.

The same benefits apply here, namely removing the need for the following
pattern in board `.kconfig` files:
```
configdefault ADC
    default y if SENSOR
```

Signed-off-by: Jordan Yates <jordan@embeint.com>