dt-bindings: rtc: ds3231: Remove text binding

The "maxim,ds3231" compatible is described in the rtc-ds1307.yaml, so
there is no need to keep the text bindings version.

Remove the maxim,ds3231.txt file in favor of the rtc-ds1307.yaml binding.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230902134407.2589099-1-festevam@gmail.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/maxim,ds3231.txt

-* Maxim DS3231 Real Time Clock
-
-Required properties:
-- compatible: Should contain "maxim,ds3231".
-- reg: I2C address for chip.
-
-Optional property:
-- #clock-cells: Should be 1.
-- clock-output-names:
-  overwrite the default clock names "ds3231_clk_sqw" and "ds3231_clk_32khz".
-
-Each clock is assigned an identifier and client nodes can use this identifier
-to specify the clock which they consume. Following indices are allowed:
-    - 0: square-wave output on the SQW pin
-    - 1: square-wave output on the 32kHz pin
-
-- interrupts: rtc alarm/event interrupt. When this property is selected,
-  clock on the SQW pin cannot be used.
-
-Example:
-
-ds3231: ds3231@51 {
-	compatible = "maxim,ds3231";
-	reg = <0x68>;
-	#clock-cells = <1>;
-};
-
-device1 {
-...
-	clocks = <&ds3231 0>;
-...
-};
-
-device2 {
-...
-	clocks = <&ds3231 1>;
-...
-};