drm: bridge: Mark deprecated operations in drm_bridge_funcs

drm_bridge_funcs includes several duplicated operations as atomic
variants have been added over time.
New bridge drivers shall use the atomic variants - mark the deprecated
operations to try to avoid usage in new bridge drivers.

v2:
  - Drop out-dated comment about state in mode_set (Laurent)
  - Added missing "the" in a description

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210710084240.281063-1-sam@ravnborg.org