ASoC: dapm: Add support for multi-CODEC CODEC to CODEC links

Currently multi-CODEC is not supported on CODEC to CODEC links.
There are common applications where this would be useful, such
as connecting two mono amplifiers to an audio CODEC. Adding
support simply requires an update of snd_soc_dai_link_event
to loop over the attached CODEC DAIs.

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