tgt-vvp: Fix syntax when using multiple events for non-blocking event control

When multiple events are used in a non-blocking event control they need to
be combined into a single event using `event/or`.

The generated `event/or` statement is missing the trailing semicolon and
newline, which results in parser error when vvp tries to run.

E.g.

```
event e, f;
integer x;
x <= @(e or f) 10;
```

Add the missing semicolon and newline to fix this.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

tgt-vvp/vvp_process.c

@@ -505,6 +505,8 @@ static int show_stmt_assign_nb(ivl_statement_t net)
 			ev = ivl_stmt_events(net, idx);
 			fprintf(vvp_out, ", E_%p", ev);
 		  }
+
+		  fprintf(vvp_out, ";\n");
 		  snprintf(name, sizeof(name), "Eassign_%u", cascade_counter);
 		  cascade_counter += 1;
 	    }