ARM: dts: meson8: add the ARM TWD timer

The Meson8 and Meson8m2 SoC are using four ARM Cortex-A9 cores which
come with a "TWD" (Timer-Watchdog) based timer. This adds support for
the ARM TWD Timer on these two SoCs.
Suggested-by: Carlo Caione <carlo@endlessm.com>
[ rebased patch from Carlo, use IRQ_TYPE_EDGE_RISING instead of
  IRQ_TYPE_LEVEL_LOW to prevent "GIC: PPI13 is secure or misconfigured"
  message during boot, use pre-processor macros to specify the IRQ,
  added the correct clock, dropped TWD watchdog node since there's no
  driver for it anymore ]
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm/boot/dts/meson8.dtsi

@@ -362,6 +362,13 @@ scu@0 {
 		compatible = "arm,cortex-a9-scu";
 		reg = <0x0 0x100>;
 	};
+
+	timer@600 {
+		compatible = "arm,cortex-a9-twd-timer";
+		reg = <0x600 0x20>;
+		interrupts = <GIC_PPI 13 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_EDGE_RISING)>;
+		clocks = <&clkc CLKID_PERIPH>;
+	};
 };
 
 &pwm_ab {