dt-bindings: Add max12xx SPI ADC series as trivial devices

Update the compatible list with three Maxim ADCs compatibles.

Signed-off-by: Miquel Raynal <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/devicetree/bindings/trivial-devices.yaml

···
           - maxim,max1029
             # 10-bit 16 channels 300ks/s SPI ADC with temperature sensor
           - maxim,max1031
+            # 12-bit 8 channels 300ks/s SPI ADC with temperature sensor
+          - maxim,max1227
+            # 12-bit 12 channels 300ks/s SPI ADC with temperature sensor
+          - maxim,max1229
+            # 12-bit 16 channels 300ks/s SPI ADC with temperature sensor
+          - maxim,max1231
             # Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCs
           - maxim,max1237
             # PECI-to-I2C translator for PECI-to-SMBus/I2C protocol conversion