ASoC: hdmi-codec: make hdmi_codec_controls static

ASoC: hdmi-codec: make hdmi_codec_controls static

This symbol is not used outside of hdmi-codec.c, so marks it static.

Fix the following sparse warning:

sound/soc/codecs/hdmi-codec.c:750:25: warning: symbol
'hdmi_codec_controls' was not declared. Should it be static?

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Link: https://lore.kernel.org/r/1623822941-3077-1-git-send-email-jiapeng.chong@linux.alibaba.com
Signed-off-by: Mark Brown <broonie@kernel.org>