drm/bridge: adv7511: clean up CEC adapter when probe fails

When the probe routine fails we also need to clean up the
CEC adapter registered in adv7511_cec_init().

Fixes: 3b1b9750 ("drm: adv7511/33: add HDMI CEC support")
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220321104705.2804423-1-l.stach@pengutronix.de