cs42l83_regmap is only used in cs42l83-i2c.c now, change it to static.

Fixes: 94d5f62a ("ASoC: cs42l83: Extend CS42L42 support to new part")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220921153123.1508144-1-yangyingliang@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>