Fix Writeback stage lint errors

- unpacked array decending order
- unspecified generate block

Signed-off-by: Eunchan Kim <eunchan@opentitan.org>

rtl/ibex_wb_stage.sv

@@ -51,7 +51,7 @@ module ibex_wb_stage #(
 
   // 0 == RF write from ID
   // 1 == RF write from LSU
-  logic [31:0] rf_wdata_wb_mux    [1:0];
+  logic [31:0] rf_wdata_wb_mux    [2];
   logic [1:0]  rf_wdata_wb_mux_we;
 
   if(WritebackStage) begin : g_writeback_stage
@@ -115,7 +115,7 @@ module ibex_wb_stage #(
     // rf_wdata_wb_q is used rather than rf_wdata_wb_o as the latter includes read data from memory
     // that returns too late to be used on the forwarding path.
     assign rf_wdata_fwd_wb_o = rf_wdata_wb_q;
-  end else begin
+  end else begin : g_bypass_wb
     // without writeback stage just pass through register write signals
     assign rf_waddr_wb_o         = rf_waddr_id_i;
     assign rf_wdata_wb_mux[0]    = rf_wdata_id_i;