ALSA: usb-audio - Added functionality for E-mu 0404USB/0202USB/TrackerPre

Added functionality:
1) Extension Units support (all XU settings now available at alsamixer,
   kmix, etc):
- "AnalogueIn soft limiter" switch;
- "Sample rate" selector (values 0,1,2,3,4,5 corresponds to 44.1 48 ...
  192 kHz);
- "DigitalIn CLK source" selector (internal/external) (**);
- "DigitalOut format SPDIF/AC3" switch (**);
(**)E-mu-0404usb only.

2) Automatic device sample rate adjustment depending on substream
   samplerate for both capture and playback substream.

[minor coding-style fixes by tiwai]

Signed-off-by: Sergiy Kovalchuk <cnb_zerg@yahoo.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/usbaudio.h

@@ -208,6 +208,16 @@ struct snd_usb_midi_endpoint_info {
 /*
  */
 
+/*E-mu USB samplerate control quirk*/
+enum {
+	EMU_QUIRK_SR_44100HZ = 0,
+	EMU_QUIRK_SR_48000HZ,
+	EMU_QUIRK_SR_88200HZ,
+	EMU_QUIRK_SR_96000HZ,
+	EMU_QUIRK_SR_176400HZ,
+	EMU_QUIRK_SR_192000HZ
+};
+
 #define combine_word(s)    ((*(s)) | ((unsigned int)(s)[1] << 8))
 #define combine_triple(s)  (combine_word(s) | ((unsigned int)(s)[2] << 16))
 #define combine_quad(s)    (combine_triple(s) | ((unsigned int)(s)[3] << 24))
@@ -233,6 +243,9 @@ void snd_usbmidi_input_stop(struct list_head* p);
 void snd_usbmidi_input_start(struct list_head* p);
 void snd_usbmidi_disconnect(struct list_head *p);
 
+void snd_emuusb_set_samplerate(struct snd_usb_audio *chip,
+			unsigned char samplerate_id);
+
 /*
  * retrieve usb_interface descriptor from the host interface
  * (conditional for compatibility with the older API)