VT1802 codec seems to reset EAPD of other pins in the hardware level,
and this was another reason of the silent headphone output on some
machines.  As a workaround, introduce a new flag indicating to keep
the EPAD on to the generic parser, and set it in patch_via.c.
Reported-by: Alex Riesen <raa.lkml@gmail.com>
Cc: <stable@vger.kernel.org> [v3.9]
Signed-off-by: Takashi Iwai <tiwai@suse.de>