drm/bridge: sii902x: Fix audio codec unregistration

The driver never unregisters the audio codec platform device, which can
lead to a crash on module reloading, nor does it handle the return value
from sii902x_audio_codec_init().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Fixes: ff578163

 ("drm/bridge: sii902x: Implement HDMI audio support")
Cc: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Aradhya Bhatia <a-bhatia1@ti.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240103-si902x-fixes-v1-2-b9fd3e448411@ideasonboard.com