Field with wrong buffer was used to make sort key, which results in producing
same sort key for all records.



sql/filesort.cc:
  Fix bug#7422 "order by" doesn't work
mysql-test/t/view.test:
  Test case for bug#7422 "order by" doesn't work
mysql-test/r/view.result:
  Test case for bug#7422 "order by" doesn't work