dt-bindings: iio: adc: exynos-adc: require second interrupt with touch screen

The ADC in S3C/S5P/Exynos SoCs can be used also for handling touch
screen.  In such case the second interrupt is required.  This second
interrupt can be anyway provided, even without touch screens.  This
fixes dtbs_check warnings like:

  arch/arm/boot/dts/s5pv210-aquila.dt.yaml: adc@e1700000: interrupts: [[23], [24]] is too long
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huwei.com>
Link: https://lore.kernel.org/r/20200910161933.9156-1-krzk@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/samsung,exynos-adc.yaml

@@ -41,7 +41,10 @@ properties:
     maxItems: 2
 
   interrupts:
-    maxItems: 1
+    description:
+      ADC interrupt followed by optional touchscreen interrupt.
+    minItems: 1
+    maxItems: 2
 
   "#io-channel-cells":
     const: 1
@@ -107,6 +110,15 @@ allOf:
           items:
             - const: adc
 
+  - if:
+      required:
+        - has-touchscreen
+    then:
+      properties:
+        interrupts:
+          minItems: 2
+          maxItems: 2
+
 examples:
   - |
     adc: adc@12d10000 {