Controls on a path only have an effect if the sink on the path is either a
mixer or mux widget. Currently we sort of silently ignore controls on other
paths, but since they don't do anything having them on other paths does not
make much sense and it is probably safe to assume that if we see such a path
it is a mistake in the driver that registered the path. This patch modifies
snd_soc_dapm_add_path() to report an error if a path with and control is
encountered where we didn't expect a control. This also allows to simplify
the code quite a bit.

The patch also moves the connecting of the path lists out of
dapm_connect_mux() and dapm_connect_mixer() into snd_soc_dapm_add_path().
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>