dt-bindings: iio: add missing reset-gpios constrain

The Documentation/devicetree/bindings/gpio/gpio-consumer-common.yaml
schema does not enforce number of reset GPIOs, thus each device binding
must do it.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/devicetree/bindings/iio/addac/adi,ad74115.yaml

···
 
   spi-cpol: true
 
-  reset-gpios: true
+  reset-gpios:
+    maxItems: 1
 
   interrupts:
     minItems: 1

Documentation/devicetree/bindings/iio/dac/adi,ad5758.yaml

···
           - const: -1000
           - const: 22000
 
-  reset-gpios: true
+  reset-gpios:
+    maxItems: 1
 
   adi,dc-dc-ilim-microamp:
     enum: [150000, 200000, 250000, 300000, 350000, 400000]

Documentation/devicetree/bindings/iio/health/ti,afe4403.yaml

···
     maxItems: 1
     description: Connected to ADC_RDY pin.
 
-  reset-gpios: true
+  reset-gpios:
+    maxItems: 1
 
 required:
   - compatible

Documentation/devicetree/bindings/iio/health/ti,afe4404.yaml

···
     maxItems: 1
     description: Connected to ADC_RDY pin.
 
-  reset-gpios: true
+  reset-gpios:
+    maxItems: 1
 
 additionalProperties: false