The via-[am]c97 code is supposed to implement the audio part of VIA
south bridge chips so it is better placed under hw/audio/. Split it
off into a separate file.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <af083634e3b9efe67e6c4247cf0185d3fa7b1810.1609584216.git.balaton@eik.bme.hu>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>