CX20549 (ctx5045) doesn't accept data on index 1 for output pins,
as shown in the following hda-var transaction:

  $ hda-verb /dev/snd/hwC0D0 0x10 set_amp_gain 0xb126
  nid = 0x10, verb = 0x300, param = 0xb126
  value = 0x0
  $ hda-verb /dev/snd/hwC0D0 0x10 get_amp_gain 0x8001
  nid = 0x10, verb = 0xb00, param = 0x8001
  value = 0x0
Signed-off-by: Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>