dt-bindings: iio: adc: Add docs for LTC2499

Update the bindings documentation for ltc2497 to include the ltc2499.
Signed-off-by: Ciprian Regus <ciprian.regus@analog.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220916140922.2506248-3-ciprian.regus@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/lltc,ltc2497.yaml

@@ -13,10 +13,14 @@ description: |
   16bit ADC supporting up to 16 single ended or 8 differential inputs.
   I2C interface.
 
+  https://www.analog.com/media/en/technical-documentation/data-sheets/2497fb.pdf
+  https://www.analog.com/media/en/technical-documentation/data-sheets/2499fe.pdf
+
 properties:
   compatible:
-    const:
-      lltc,ltc2497
+    enum:
+      - lltc,ltc2497
+      - lltc,ltc2499
 
   reg: true
   vref-supply: true