ALSA: virtuoso: add de-emphasis control

Add control for the de-emphasis filter in the PCM179x DACs

Signed-off-by: Tom Yan <tom.ty89@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/oxygen/pcm1796.h

@@ -10,7 +10,6 @@
 #define PCM1796_MUTE		0x01
 #define PCM1796_DME		0x02
 #define PCM1796_DMF_MASK	0x0c
-#define PCM1796_DMF_DISABLED	0x00
 #define PCM1796_DMF_48		0x04
 #define PCM1796_DMF_441		0x08
 #define PCM1796_DMF_32		0x0c