drm/sysfs: Register "ddc" symlink later

drm/sysfs: Register "ddc" symlink later

Currently drm_sysfs_connector_add() attempts to register
the "ddc" symlink (based one connector->ddc) before the
driver's .early_register() hook has been called. That is
too early for i915 which only fully registers the aux ch
and associated i2c bus from said hook (to prevent half
initialized stuff getting exposed to userspace). This
causes my attempt at using drm_connector_init_with_ddc()
to fail, and the entire connector disappears from sysfs
on account of sysfs_create_link() failing.

To fix that split the sysfs symlink stuff into separate
functions (drm_sysfs_connector_add_late() and
drm_sysfs_connector_remove_early()) which are called
on the opposite side of the .later_register() and
.early_unregister() hooks.

Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829113920.13713-3-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de> #irc