ALSA: hda - Keep EAPD turned on for old Conexant chips

In the old Conexant chips (5045, 5047, 5051 and 5066), a single EAPD
may handle both headphone and speaker outputs while it's assigned only
to one of them.  Turning off dynamically leads to the unexpected silent
output in such a configuration with the auto-mute function.

Since it's difficult to know how the EAPD is handled in the actual h/w
implementation, better to keep EAPD on while running for such codecs.

Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>