Separated manager and subordinate drivers

Other clean up and changes

src/axi/axi_transaction.sv

@@ -1,10 +1,10 @@
 // ----------------------------------------------------------------------
 class axi_transaction extends uvm_sequence_item;
     // Declare AXI transaction fields
-    rand axi_transaction_type_t txn_type; // Transaction type (read/write)
-    rand bit [31:0] addr; // Address
-    rand bit [31:0] data; // Data
-    rand bit [3:0]  strb; // Byte enable
+    rand axi_transaction_type_t     txn_type; // Transaction type (read/write)
+    rand bit [`ADDR_WIDTH-1:0]        addr; // Address
+    rand bit [`DATA_WIDTH-1:0]        data; // Data
+    rand bit [`DATA_WIDTH_DIV_8-1:0]  strb; // Byte enable
 
     `uvm_object_utils_begin(axi_transaction)
         `uvm_field_enum(axi_transaction_type_t, txn_type, UVM_DEFAULT)