Some adjustments to the recent dsched removal.

Some adjustments to the recent dsched removal.

* Make 'options DSCHED_FQ' a no-op for now. It used to be in our
  default config, so give people some time to edit their custom
  configs derived from X86_64_GENERIC, like we did for other such
  options. It will be completely removed at a later point in time
  after the release.

* Add a quick note to UPGRADING about this.

* While here, remove associated manual pages and MLINKS too.