ASoC: core: If component doesn't have of_node use parent's node instead

If an ASoC component device does not have a device tree node, use its
parent's node instead, when looking for a matching DAI based on a
device tree reference.

This allows video device drivers to register a separate child device
for their ASoC side audio functionality.  [And MFDs in general --
broonie]

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>