ASoC: max9860: fix non static symbol warnings

Fixes the following sparse warnings:

sound/soc/codecs/max9860.c:120:28: warning:
 symbol 'max9860_regmap' was not declared. Should it be static?
sound/soc/codecs/max9860.c:596:25: warning:
 symbol 'max9860_pm_ops' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Mark Brown <broonie@kernel.org>