Added header guards to prevent errors from double-inclusions

modules/lu.sv

@@ -1,3 +1,5 @@
+`ifndef LU_H_SV
+`define LU_H_SV
 module lu #(parameter width = 2) (
     input logic [1:0] op,
     input logic [2**width-1:0] A,
@@ -13,4 +15,5 @@ module lu #(parameter width = 2) (
 			default: Y = '0;
 		endcase
     end
-endmodule
+endmodule
+`endif