sof-soundwire: fix speaker init include for combined codecs

[GitHub pull_request - opened <github@alsa-project.org>]

alsa-project/alsa-ucm-conf pull request #855 was opened from pgavin:

Since commit cd342774cd02 ("sof-soundwire: cleanups for codecs with multiple functions") the speaker init filter regex is not anchored, so a combined speaker codec string like rt721+rt1320 or rt712+rt1320 also matches the single codec names from MultiCodecRegex. The config then tries to include codecs/rt721+rt1320/init.conf, which does not exist, and the whole UCM configuration fails to load:

  could not open configuration file .../ucm2/codecs/rt721+rt1320/init.conf
  failed to import hw:1 use case configuration -2

PipeWire falls back to a stereo profile on PCM 0 and the internal speakers (PCM 2) are never used.

Guard the regex with "=" like the other multi-codec checks, so only exact codec names with a codecs/<name>/init.conf are included. The combined codecs keep using sof-soundwire/<spk>.conf from HiFi.conf, and the rt721 codec init is still included via the headset codec, as before the cleanup.

Tested on Razer Blade 16 (RZ09-0581) with components:
  cfg-amp:2 mic:dmic cfg-mics:2 iec61937-pcm:7,6,5 hs:rt721 spk:rt721+rt1320

Request URL   : https://github.com/alsa-project/alsa-ucm-conf/pull/855
Patch URL     : https://github.com/alsa-project/alsa-ucm-conf/pull/855.patch
Repository URL: https://github.com/alsa-project/alsa-ucm-conf