"100ns" -> "100 ns" to prevent modelsim compilation warning

applications/lofar2/designs/lofar2_unb2b_adc/tb/vhdl/tb_lofar2_unb2b_adc_multichannel.vhd

@@ -420,7 +420,7 @@ BEGIN
   ------------------------------------------------------------------------------
   proc_read_avs_regs : PROCESS
   BEGIN
-    wait for 100ns;
+    wait for 100 ns;
     avs_address(0) <= (others => '0');
     avs_chipselect(0) <= '0';
     avs_read(0) <= '0';