ASoC: Intel: update bxt_da7219_max98357a to support quad ch dmic capture

This patch updates FE channel constraints & BE fixup to support
quad channel DMIC capture.
DMIC pin's BE fixup is configured based on channel input, i.e.
either stereo or quad.

Signed-off-by: Sathyanarayana Nujella <sathyanarayana.nujella@intel.com>
Signed-off-by: Harsha Priya <harshapriya.n@intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>