remove unnecessary second call to static_unwrap_type in ada_evaluate_subexp

remove unnecessary second call to static_unwrap_type in ada_evaluate_subexp

In ada-lang.c::ada_evaluate_subexp, case OP_VAR_VALUE, when noside
is EVAL_AVOID_SIDE_EFFECTS, the first thing we do is set type as
follow:

    type = static_unwrap_type (SYMBOL_TYPE (exp->elts[pc + 2].symbol));

Later on in the same block, we make the same call:

    return value_zero
      (to_static_fixed_type
       (static_unwrap_type (SYMBOL_TYPE (exp->elts[pc + 2].symbol))),
       not_lval);

This patch removes the second call, since it should result in the same
type being returned, so no point in making that call again.

gdb/ChangeLog:

        * ada-lang.c (ada_evaluate_subexp) <OP_VAR_VALUE>: Remove
        unnecessary second call to static_unwrap_type.