dt-bindings: rtc: sun6i-rtc: Fix register range in example

The register range for the RTC extends beyond 0x54.
Use the size from the user manual's memory map instead.

Fixes: 9765d2d9 ("rtc: sun6i: Add sun6i RTC driver")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/sun6i-rtc.txt

@@ -38,7 +38,7 @@ Example:
 
 rtc: rtc@1f00000 {
 	compatible = "allwinner,sun6i-a31-rtc";
-	reg = <0x01f00000 0x54>;
+	reg = <0x01f00000 0x400>;
 	interrupts = <0 40 4>, <0 41 4>;
 	clock-output-names = "osc32k";
 	clocks = <&ext_osc32k>;