ASoC: sun8i-codec-analog: split regmap code into separate driver

It will be reused by sun50i-codec-analog later.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Mark Brown <broonie@kernel.org>