ALSA: HDA: Add a new Conexant codec 506e (20590)

Conexant 506e/20590 has the same graph as the rest of the 5066 family.

BugLink: http://bugs.launchpad.net/bugs/723672



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