drm/arc: Inline remaining files

At less than 500 lines total feels like the right thing to do.

Also noticed that the simple wrapper around drm_connector_cleanup can
be dropped.

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210112084358.2771527-13-daniel.vetter@ffwll.ch