When the HDMI unbinds drm_connector_cleanup() and drm_encoder_cleanup()
are called. This also happens when the connector and the encoder are
destroyed. This double call triggers a NULL pointer exception.

The patch fixes this by removing the cleanup calls in the unbind
function.

Cc: <stable@vger.kernel.org>
Fixes: 9c568101 ("drm/sun4i: Add HDMI support")
Signed-off-by: Stefan Mavrodiev <stefan@olimex.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20191217124632.20820-1-stefan@olimex.com