It turns out that U-Boot exposes a different name to ALSA UCM. Fix the symlink to be the correct name from SMBIOS data. Add the missing PlaybackMixer line. Without it, ALSA doesn't select the right mixer, leading to a Qualcomm DSP error. Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/8624>