Add ADC support for the sun8i-codec driver.

This driver uses microphones widgets and routes provided by the
analog part (sun8i-codec-analog).
Some digital configurations are needed by creating new ADC widgets
and routes.
Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>