ASoC: core: Allow codec_conf DT lookups to match parent of_node

For devices implemented as a MFD it is common to only have a single node
in devicetree representing the whole device. As such when looking up
codec_conf mappings we should match against both the devices of_node and
the devices parent's of_node, as is already done for DAIs and platform
components.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>