feat(L09): add load and store semantics card

tests/task03_load_store_unit_tb.sv

@@ -0,0 +1,24 @@
+module tb;
+    logic clk=0, request=0, write_enable=0;
+    logic [31:0] address=0, write_data=0, read_data;
+    logic [2:0] funct3=0;
+    logic fault;
+    string trace_file;
+    load_store_unit dut (.*);
+    always #1 clk=~clk;
+    task automatic store(input logic [31:0] addr, input logic [2:0] size, input logic [31:0] data);
+        @(negedge clk); request=1; write_enable=1; address=addr; funct3=size; write_data=data;
+        @(posedge clk); #1;
+    endtask
+    initial begin
+        if ($value$plusargs("trace=%s", trace_file)) begin $dumpfile(trace_file); $dumpvars(0, tb); end
+        store(0,2,32'h11223344); store(1,0,32'haa);
+        @(negedge clk); write_enable=0; address=0; funct3=2; #1;
+        if(read_data!==32'h1122aa44||fault)$fatal(1,"FAIL word=%h",read_data);
+        address=1; funct3=0; #1; if(read_data!==32'hffffffaa||fault)$fatal(1,"FAIL LB=%h",read_data);
+        funct3=4; #1; if(read_data!==32'haa||fault)$fatal(1,"FAIL LBU=%h",read_data);
+        address=2; funct3=2; #1; if(!fault||read_data!==0)$fatal(1,"FAIL fault=%b data=%h",fault,read_data);
+        $display("PASS task03 word=1122aa44 lb=ffffffaa lbu=000000aa fault=1");
+        $finish;
+    end
+endmodule