ARC: [dts] add cpu nodes to ARCHS SMP device tree

Trying to get clock for CPU cores on SMP systems I found that I was only
able to get clock for core[0]. That was because only one cpu@0 node was
represented in ARC HS device tree and it was impossible to get clock for
"non-existing" cores.

So as ARC HS may have up to 4 cores we update device tree to match
maximum possible cores quantity.
Signed-off-by: Vlad Zakharov <vzakhar@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/boot/dts/skeleton_hs_idu.dtsi

@@ -19,10 +19,28 @@ cpus {
 
 		cpu@0 {
 			device_type = "cpu";
-			compatible = "snps,archs38xN";
+			compatible = "snps,archs38";
 			reg = <0>;
 			clocks = <&core_clk>;
 		};
+		cpu@1 {
+			device_type = "cpu";
+			compatible = "snps,archs38";
+			reg = <1>;
+			clocks = <&core_clk>;
+		};
+		cpu@2 {
+			device_type = "cpu";
+			compatible = "snps,archs38";
+			reg = <2>;
+			clocks = <&core_clk>;
+		};
+		cpu@3 {
+			device_type = "cpu";
+			compatible = "snps,archs38";
+			reg = <3>;
+			clocks = <&core_clk>;
+		};
 	};
 
 	/* TIMER0 with interrupt for clockevent */