dt-bindings: iio: adc: ti,ads1015: fix datarate max value and meaning

Datarate (dr) is a 3-bit wide register field. Values from 0 to 7 are
allowed for all devices but only for the ADS1115 devices a value of 7
does make a difference.

While on it fix the description of the datarate for ADS1115 devices as
well.
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230621160857.3400747-1-m.felsch@pengutronix.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/ti,ads1015.yaml

@@ -78,9 +78,9 @@ patternProperties:
       ti,datarate:
         $ref: /schemas/types.yaml#/definitions/uint32
         minimum: 0
-        maximum: 6
+        maximum: 7
         description: |
-          Data acquisition rate in samples per second
+          Data acquisition rate in samples per second for ADS1015, TLA2024
           0: 128
           1: 250
           2: 490
@@ -88,6 +88,17 @@ patternProperties:
           4: 1600 (default)
           5: 2400
           6: 3300
+          7: 3300
+
+          Data acquisition rate in samples per second for ADS1115
+          0: 8
+          1: 16
+          2: 32
+          3: 64
+          4: 128 (default)
+          5: 250
+          6: 475
+          7: 860
 
     required:
       - reg