ALSA: usb-audio: refactor code

Clean up the usb audio driver by factoring out a lot of functions to
separate files. Code for procfs, quirks, urbs, format parsers etc all
got a new home now.

Moved almost all special quirk handling to quirks.c and introduced new
generic functions to handle them, so the exceptions do not pollute the
whole driver.

Renamed usbaudio.c to card.c because this is what it actually does now.
Renamed usbmidi.c to midi.c for namespace clarity.
Removed more things from usbaudio.h.

The non-standard drivers were adopted accordingly.

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/pcm.h b/sound/usb/pcm.h
new file mode 100644
index 0000000..8585601
--- /dev/null
+++ b/sound/usb/pcm.h
@@ -0,0 +1,14 @@
+#ifndef __USBAUDIO_PCM_H
+#define __USBAUDIO_PCM_H
+
+void snd_usb_set_pcm_ops(struct snd_pcm *pcm, int stream);
+
+int snd_usb_init_pitch(struct usb_device *dev, int iface,
+		       struct usb_host_interface *alts,
+		       struct audioformat *fmt);
+
+int snd_usb_init_sample_rate(struct usb_device *dev, int iface,
+			     struct usb_host_interface *alts,
+			     struct audioformat *fmt, int rate);
+
+#endif /* __USBAUDIO_PCM_H */