drm/doc: More fine-tuning on userspace review requirements

With Eric's patch

commit ba6e798e
Author: Eric Anholt <eric@anholt.net>
Date:   Wed Apr 24 11:56:17 2019 -0700

    drm/doc: Document expectation that userspace review looks at kernel uAPI.

there's been concerns raised that we expect userspace people to do
in-depth kernel patch review. That's not reasonable, same way kernel
people can't review all the userspace we have. Try to clarify
expectations a bit more.

Cc: Eric Anholt <eric@anholt.net>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Cc: contact@emersion.fr
Cc: wayland-devel@lists.freedesktop.org
Acked-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190521084849.27452-1-daniel.vetter@ffwll.ch