dt-bindings: timer: Document Owl timer

The Actions Semi S500 SoC contains a timer block with two 2 Hz and two
32-bit timers. The S900 SoC timer block has four 32-bit timers.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

Documentation/devicetree/bindings/timer/actions,owl-timer.txt

+Actions Semi Owl Timer
+
+Required properties:
+- compatible      :  "actions,s500-timer" for S500
+                     "actions,s900-timer" for S900
+- reg             :  Offset and length of the register set for the device.
+- interrupts      :  Should contain the interrupts.
+- interrupt-names :  Valid names are: "2hz0", "2hz1",
+                                      "timer0", "timer1", "timer2", "timer3"
+                     See ../resource-names.txt
+
+Example:
+
+		timer@b0168000 {
+			compatible = "actions,s500-timer";
+			reg = <0xb0168000 0x100>;
+			interrupts = <GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH>,
+			             <GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>;
+			interrupt-names = "timer0", "timer1";
+		};