at86rf230: add warning if edge-triggered irq

While testing I experience a deadlock while using the at86rf233 on a
raspberry pi. The reason was an edge triggered gpio irq because the irq
triggered while irq was disabled. This issue doesn't happend on a level
triggered irq because the irq will hit after calling enable_irq.

This patch adds a warning that it's not recommended to use a edge-triggered
irq type. Also change the examples to high-level irqtype.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

Documentation/devicetree/bindings/net/ieee802154/at86rf230.txt

@@ -6,7 +6,8 @@ Required properties:
   - spi-max-frequency:	maximal bus speed, should be set to 7500000 depends
 			sync or async operation mode
   - reg:		the chipselect index
-  - interrupts:		the interrupt generated by the device
+  - interrupts:		the interrupt generated by the device. Non high-level
+			can occur deadlocks while handling isr.
 
 Optional properties:
   - reset-gpio:		GPIO spec for the rstn pin
@@ -20,7 +21,7 @@ Example:
 		compatible = "atmel,at86rf231";
 		spi-max-frequency = <7500000>;
 		reg = <0>;
-		interrupts = <19 1>;
+		interrupts = <19 4>;
 		interrupt-parent = <&gpio3>;
 		xtal-trim = /bits/ 8 <0x06>;
 	};