ASoC: atmel: tse850: rely on the ssc to register as a cpu dai by itself

This breaks devicetree compatibility, but in this case that is ok. All
affected units are either on my desk, or running an even older version
of the driver that is not compatible with the upstreamed version anyway
(and when these other units are eventually updated, they will get a
fresh dtb as well, so that is not a significant problem either).

All of that is of course assuming that noone else has managed to build
something that can use this driver, but that seems extremely improbable.

Signed-off-by: Peter Rosin <peda@axentia.se>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>