ALSA: ice1724: Use linear scale for AK4396 volume control.

The AK4396 DAC has a linear-scale attentuator, but
sound/pci/ice1712/prodigy_hifi.c used a log scale instead, which is
not quite right.  This patch restores the correct scale, borrowing
from the ak4396 code in sound/pci/oxygen/oxygen.c.
Signed-off-by: Matteo Frigo <athena@fftw.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/ice1712/prodigy_hifi.c

@@ -297,6 +297,7 @@ static int ak4396_dac_vol_put(struct snd_kcontrol *kcontrol, struct snd_ctl_elem
 }
 
 static const DECLARE_TLV_DB_SCALE(db_scale_wm_dac, -12700, 100, 1);
+static const DECLARE_TLV_DB_LINEAR(ak4396_db_scale, TLV_DB_GAIN_MUTE, 0);
 
 static struct snd_kcontrol_new prodigy_hd2_controls[] __devinitdata = {
     {
@@ -307,7 +308,7 @@ static struct snd_kcontrol_new prodigy_hd2_controls[] __devinitdata = {
 	.info = ak4396_dac_vol_info,
 	.get = ak4396_dac_vol_get,
 	.put = ak4396_dac_vol_put,
-	.tlv = { .p = db_scale_wm_dac },
+	.tlv = { .p = ak4396_db_scale },
     },
 };