ASoC: sn95031: add capture support

This patch adds the support for capture path in sn95031 codec.
This codec supports upto 6DMICs, 2 AMICs and Linein. The linein and AMICs
are connected through a MUX to ADC. The TX paths can be assigned to any of the
ADCs or DMICs.

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Harsha Priya <priya.harsha@intel.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>