dts: versatile: Add sysregs node

The Versatile boards have the same sysregs as other ARM Ltd boards. Add
the nodes in order to enable support for 24MHz counter as sched_clock.

This is a minimal node definition as the existing sub node definition
used on VExpress has some issues raised by Linus W.
Signed-off-by: NRob Herring <robh@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>

arch/arm/boot/dts/versatile-ab.dts

@@ -252,6 +252,11 @@
 			#size-cells = <1>;
 			ranges = <0 0x10000000 0x10000>;
 
+			sysreg@0 {
+				compatible = "arm,versatile-sysreg", "syscon";
+				reg = <0x00000 0x1000>;
+			};
+
 			aaci@4000 {
 				compatible = "arm,primecell";
 				reg = <0x4000 0x1000>;