MAINTAINERS: drm/ci: add entries for xfail files

MAINTAINERS: drm/ci: add entries for xfail files

DRM CI keeps track of which tests are failing, flaking or being skipped
by the ci in the expectations files. Add entries for those files to the
corresponding driver maintainer, so they can be notified when they
change.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20230919182249.153499-1-helen.koike@collabora.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>