ALSA: cs46xx: Fix Duplicate front for CS4294 and CS4298 codecs

Currently, the Duplicate front control is enabled only for two specific
revisions of CS4294.

Enable it for all CS4294 and CS4298 codecs instead.

This fixes rear output on my VC-4620N sound card
(CS4620 + CS4298 rev.5).

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>