ALSA: usb-mixer: factor out quirks

Move all non-standard mixer controls and vendor-specific extensions to a
separate file. Some structs need to be exported now.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 0c0b23b..a82cfed 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -25,6 +25,7 @@
 #include "usbaudio.h"
 #include "card.h"
 #include "usbmixer.h"
+#include "mixer_quirks.h"
 #include "midi.h"
 #include "quirks.h"
 #include "helper.h"