ASoC: byt-rt5640: Register microphone routes with the card DAPM context

Board level DAPM elements should be registered with the card's DAPM context
rather than the CODEC's DAPM context.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>