doc: HACK: Move the docs under doc/ so that we can build

Otherwise, I get this on install:

NotADirectoryError: [Errno 20] Not a directory: '/home/anholt/src/xserver/build/xserver-doc/html/assets/js/search/hotdoc_fragments/../hw/xfree86'

Signed-off-by: Eric Anholt <eric@anholt.net>
3 jobs for docs in 1 minute and 26 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Docker Image
failed #218157
debian-testing

00:01:26

 
  Build And Test
skipped #218158
autotools-build-and-test
skipped #218159
meson-build-and-test
 
Name Stage Failure
failed
debian-testing Docker Image
      File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'setuptools'

----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-mbaym4wg/hotdoc/
error while running runtime: exit status 1
Running after script...
$ if [[ ! -e .success ]] ; then exit 0; fi
ERROR: Job failed: exit code 1