dt-bindings: pwm: ti,pwm-omap-dmtimer: Update binding for yaml

Update for yaml and remove the old txt binding.

As we can replace most of the custom timer API with standard Linux
frameworks such as clock framework, let's tag the properties for
ti,prescaler and ti,clock-source as deprecated.

Cc:  <linux-pwm@vger.kernel.org>
Cc: Nishanth Menon <nm@ti.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/pwm-omap-dmtimer.txt

-* OMAP PWM for dual-mode timers
-
-Required properties:
-- compatible: Shall contain "ti,omap-dmtimer-pwm".
-- ti,timers: phandle to PWM capable OMAP timer. See timer/ti,timer-dm.yaml for info
-  about these timers.
-- #pwm-cells: Should be 3. See pwm.yaml in this directory for a description of
-  the cells format.
-
-Optional properties:
-- ti,prescaler: Should be a value between 0 and 7, see the timers datasheet
-- ti,clock-source: Set dmtimer parent clock, values between 0 and 2:
-  - 0x00 - high-frequency system clock (timer_sys_ck)
-  - 0x01 - 32-kHz always-on clock (timer_32k_ck)
-  - 0x02 - external clock (timer_ext_ck, OMAP2 only)
-
-Example:
-	pwm9: dmtimer-pwm@9 {
-		compatible = "ti,omap-dmtimer-pwm";
-		ti,timers = <&timer9>;
-		#pwm-cells = <3>;
-	};

Documentation/devicetree/bindings/pwm/ti,omap-dmtimer-pwm.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/ti,omap-dmtimer-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TI dual mode timer PWM controller
+
+maintainers:
+  - Tony Lindgren <tony@atomide.com>
+
+description:
+  TI dual mode timer instances have an IO pin for PWM capability
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    const: ti,omap-dmtimer-pwm
+
+  "#pwm-cells":
+    const: 3
+
+  ti,timers:
+    description: Timer instance phandle for the PWM
+    $ref: /schemas/types.yaml#/definitions/phandle
+
+  ti,prescaler:
+    description: |
+      Legacy clock prescaler for timer. The timer counter is prescaled
+      with 2^n where n is the prescaler.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [ 0, 1, 2, 3, 4, 5, 6, 7 ]
+    deprecated: true
+
+  ti,clock-source:
+    description: |
+      Legacy clock for timer, please use assigned-clocks instead.
+      0x00 - high-frequency system clock (timer_sys_ck)
+      0x01 - 32-kHz always-on clock (timer_32k_ck)
+      0x02 - external clock (timer_ext_ck, OMAP2 only)
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [ 0, 1, 2 ]
+    deprecated: true
+
+required:
+  - compatible
+  - ti,timers
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    pwm9: pwm {
+      compatible = "ti,omap-dmtimer-pwm";
+      ti,timers = <&timer9>;
+      #pwm-cells = <3>;
+    };