init units and bins, fix 2

calc_tb.sv

@@ -20,7 +20,7 @@ covergroup cg @(posedge clk);
     bins S_MUL = {3};
     bins S_DIV = {4};
   }
-  c2: coverpoint $root.calc_dut.STATE_C;
+  c2: coverpoint $root.calc_dut::STATE_C;
 endgroup: cg
 
 cg cover_inst = new; // instatiate the cover model