ARC: [dts] Add clk feeding into timers to DTs

This allows us to introduce timers in DT in next commit

The core clk frequency hack in AXS103 platform is also extended,
where the core clk feeding into timers is updated in-place in FDT.

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/boot/dts/nsim_hs.dts

@@ -39,6 +39,12 @@
 			 bus addr,   parent bus addr, size */
 		ranges = <0x80000000 0x0 0x80000000 0x80000000>;
 
+		core_clk: core_clk {
+			#clock-cells = <0>;
+			compatible = "fixed-clock";
+			clock-frequency = <80000000>;
+		};
+
 		core_intc: core-interrupt-controller {
 			compatible = "snps,archs-intc";
 			interrupt-controller;