ALSA: HDA: Fix automute for Cirrus Logic 421x

There was a bug in the automute logic causing speakers not to
mute when headphones were plugged in.

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