dt-bindings: iio: adc: ti,tlc4541 binding conversion

Simple binding so easy to convert.
Dropped the stated value of maximum spi bus frequency as it does
not seem to correspond to the datasheet.  The value of 200kHz
is the max sampling frequency of the ADC, not the clock frequency of
the SPI bus.

Added #io-channel-cells to allow use as a provider of channels to
other devices via the consumer binding.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-By: Phil Reid <preid@electromag.com.au>
Cc: Phil Reid <preid@electromag.com.au>
Link: https://lore.kernel.org/r/20200809111753.156236-14-jic23@kernel.org

Documentation/devicetree/bindings/iio/adc/ti,tlc4541.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/ti,tlc4541.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Texas Instruments TLC4541 and similar ADCs
+
+maintainers:
+  - Phil Reid <preid@electromag.com.au>
+
+description: |
+  14/16bit single channel ADC with SPI interface.
+
+properties:
+  compatible:
+    enum:
+      - ti,tlc3541
+      - ti,tlc4541
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency: true
+
+  vref-supply: true
+
+  "#io-channel-cells":
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - vref-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "ti,tlc4541";
+            reg = <0>;
+            vref-supply = <&vdd_supply>;
+            spi-max-frequency = <200000>;
+            #io-channel-cells = <1>;
+        };
+    };
+...

Documentation/devicetree/bindings/iio/adc/ti-tlc4541.txt

-* Texas Instruments' TLC4541
-
-Required properties:
- - compatible: Should be one of
-	* "ti,tlc4541"
-	* "ti,tlc3541"
-	- reg: SPI chip select number for the device
- - vref-supply: The regulator supply for ADC reference voltage
- - spi-max-frequency: Max SPI frequency to use (<= 200000)
-
-Example:
-adc@0 {
-	compatible = "ti,tlc4541";
-	reg = <0>;
-	vref-supply = <&vdd_supply>;
-	spi-max-frequency = <200000>;
-};