ASoC: codecs: rk3308: fix building without CONFIG_OF

ASoC: codecs: rk3308: fix building without CONFIG_OF

The newly added codec has an extraneous of_match_ptr() annotation for
the ID table:

sound/soc/codecs/rk3308_codec.c:956:34: error: 'rk3308_codec_of_match' defined but not used [-Werror=unused-const-variable=]
  956 | static const struct of_device_id rk3308_codec_of_match[] = {

Remove it to avoid introducing a warning when -Wunused-const-variable
gets enabled by default:

Fixes: 4ed0915f5bc4 ("ASoC: codecs: Add RK3308 internal audio codec driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://msgid.link/r/20240404095755.650364-1-arnd@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>