ALSA: hda - Add Conexant codecs CX20721, CX20722, CX20723 and CX20724

This patch adds support for Conexant HD Audio codecs
CX20721, CX20722, CX20723 and CX20724.

Cc: stable@vger.kernel.org
BugLink: https://bugs.launchpad.net/bugs/1454656


Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>