Force-probing a connector can be slow and cause flickering. As this
affects the global KMS state, let's make it so only the DRM master
can force-probe a connector.

Non-master DRM clients won't be able to force-probe a connector
anymore. Instead, KMS will perform a regular read-only connector
query.
Signed-off-by: NSimon Ser <contact@emersion.fr>
Acked-by: NPekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210402112212.5625-1-contact@emersion.fr