ASoC: da7210: Add support for spi regmap

This patch adds support for spi regmap feature to existing da7210
driver.

Signed-off-by: Ashish Chavan <ashish.chavan@kpitcummins.com>
Signed-off-by: David Dajun Chen <dchen@diasemi.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>