Remove two unnecessary casts

I noticed a spot in ada-lang.c where the return value of
value_as_address was cast to CORE_ADDR -- a no-op cast.  I searched
and found another.  This patch fixes both.

gdb/eval.c

@@ -1685,7 +1685,7 @@ eval_op_ind (struct type *expect_type, struct expression *exp,
      BUILTIN_TYPE_LONGEST would seem to be a mistake.  */
   if (type->code () == TYPE_CODE_INT)
     return value_at_lazy (builtin_type (exp->gdbarch)->builtin_int,
-			  (CORE_ADDR) value_as_address (arg1));
+			  value_as_address (arg1));
   return value_ind (arg1);
 }