ASoC: Use DAPM context rather than CODEC when constructing sequences

DAPM widgets may be associated with non-CODEC devices so compare based
on the DAPM context rather than the CODEC pointer.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>