Documentation: dt: rtc-imxdi: security violation interrupt

Document the DryIce security violation interrupt.
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

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

@@ -8,10 +8,13 @@ Required properties:
   region.
 - interrupts: rtc alarm interrupt
 
+Optional properties:
+- interrupts: dryice security violation interrupt
+
 Example:
 
 rtc@80056000 {
 	compatible = "fsl,imx53-rtc", "fsl,imx25-rtc";
 	reg = <0x80056000 2000>;
-	interrupts = <29>;
+	interrupts = <29 56>;
 };