rename use_imm and use_PC

hw/rtl/interfaces/VX_alu_req_if.v

@@ -12,8 +12,8 @@ interface VX_alu_req_if ();
     wire [31:0]             next_PC;
     wire [`ALU_BITS-1:0]    op_type;
     wire [`MOD_BITS-1:0]    op_mod;
-    wire                    rs1_is_PC;
-    wire                    rs2_is_imm;
+    wire                    use_PC;
+    wire                    use_imm;
     wire [31:0]             imm;
     wire [`NT_BITS-1:0]     tid;
     wire [`NUM_THREADS-1:0][31:0] rs1_data;