ASoC: dapm: Break dapm_set_path_status() appart

There are three different completely independent code paths in
dapm_set_path_status(). One of them is never used at all and the other two (one
for mixers, one for MUXs) have their distincive callsites that always go onto
the same path. Breaking the function into two parts allows us to reduce the code
size and in the MUX case also do some optimizations to avoid having to calcualte
the selected item for each item again.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>