Shifting a signed constant should just return the L-value.

We already covered the case of shifting zero, but the case of
shifting a signed constant was missed.

tgt-vvp/eval_expr.c

@@ -1128,7 +1128,7 @@ static struct vector_info draw_binary_expr_lrs(ivl_expr_t exp, unsigned wid)
 	      /* Sign extend any constant begets itself, if this
 		 expression is signed. */
 	    if ((lv.base < 4) && (ivl_expr_signed(exp)))
-		  break;
+		  return lv;
 
 	    if (lv.base < 4) {
 		  struct vector_info tmp;