add Tvia cyberpro 5050 to sound/trident.c

I have hacked up the drivers/sound/trident.c to also support the TVia/IGST CyberPro5050 audio (&video) controller.

This chip is common in settop boxes. I don't know if you can buy any PCI cards "off the shelf".
I think there is still interest in support for this "old" chip (3 years old), at least in the "embedded market".

Does it make sense to include it in trident.c?

BTW, the listed maintainer [email protected] does not work any more on this driver.