alsa-profiles: use SB Audigy PCM mixer controls
Creative Labs Sound Blaster Audigy cards (snd_emu10k1 driver) expose mixer controls named 'PCM Front', 'PCM Rear', etc. in addition to the more common 'Front', 'Rear', etc. The latter seem to be intended for a stereo-to-all-speakers mirroring mode that we do not use, and have no effect when we adjust them. https://docs.kernel.org/sound/cards/audigy-mixer.html
We therefore define a custom mixer path for Audigy devices, using the PCM mixer controls.
This has been tested on an Audigy 5/Rx. Based on a brief look at the ALSA driver, I think all Audigy devices (vendor 0x1102, device 0x0004 or 0x0008) have the same PCM controls, making this change probably safe for our existing Audigy udev rules.
Relevant kernel files: sound/pci/emu10k1/emu10k1_main.c sound/pci/emu10k1/emufx.c include/sound/emu10k1.h
Fixes #2934 (closed)