sof-soundwire: cleanups for codecs with multiple functions

sof-soundwire: cleanups for codecs with multiple functions

The load mechanism assumed only one multi-codec in the system, but
we saw in #774 multiple instances of those codecs (rt1320 and rt713).

Make the load mechanism straight:

- introduce file variables
- remove shadow variables
- probe multi-codecs separately and modify the file variables
- test for duplicate file inclusion (in both sof-soundwire / HiFi configs)
- merge dmic configs for rt712,rt713 to one file

This change also improves filters for speaker/headset/mic init includes.

Closes: https://github.com/alsa-project/alsa-ucm-conf/pull/775
Link: https://github.com/alsa-project/alsa-ucm-conf/issues/774
Signed-off-by: Jaroslav Kysela <perex@perex.cz>