ALSA: usb-audio: Fix Creative VF0420 rate

Creative Live! Cam Vista IM (VF0420) reports rate of 16kHz while working
at 8kHz. The patch adds its USB ID to the existing quirk.

Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>