fix: replace UNUSEDPARAM/UNUSEDSIGNAL with UNUSED for verilator lint

Verilator does not recognize UNUSEDPARAM or UNUSEDSIGNAL.
Correct suppression code is UNUSED.

rtl/ip/PLL_2019_2/clk_pll_stub.vhdl

@@ -0,0 +1,32 @@
+-- Copyright 1986-2019 Xilinx, Inc. All Rights Reserved.
+-- --------------------------------------------------------------------------------
+-- Tool Version: Vivado v.2019.2 (lin64) Build 2708876 Wed Nov  6 21:39:14 MST 2019
+-- Date        : Tue Jun 30 01:14:25 2026
+-- Host        : fedora running 64-bit unknown
+-- Command     : write_vhdl -force -mode synth_stub
+--               /home/fallensigh/Dev/ciciec2026_loongson_regional/rtl/ip/PLL_2019_2/clk_pll_stub.vhdl
+-- Design      : clk_pll
+-- Purpose     : Stub declaration of top-level module interface
+-- Device      : xc7a200tfbg676-1
+-- --------------------------------------------------------------------------------
+library IEEE;
+use IEEE.STD_LOGIC_1164.ALL;
+
+entity clk_pll is
+  Port ( 
+    cpu_clk : out STD_LOGIC;
+    sys_clk : out STD_LOGIC;
+    resetn : in STD_LOGIC;
+    locked : out STD_LOGIC;
+    clk_in1 : in STD_LOGIC
+  );
+
+end clk_pll;
+
+architecture stub of clk_pll is
+attribute syn_black_box : boolean;
+attribute black_box_pad_pin : string;
+attribute syn_black_box of stub : architecture is true;
+attribute black_box_pad_pin of stub : architecture is "cpu_clk,sys_clk,resetn,locked,clk_in1";
+begin
+end;