ALSA: snd-usb: move code from urb.c to endpoint.c

No code altered at this point, simply preparing for upcoming
refactorizations.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/pcm.c

@@ -28,7 +28,7 @@
 #include "card.h"
 #include "quirks.h"
 #include "debug.h"
-#include "urb.h"
+#include "endpoint.h"
 #include "helper.h"
 #include "pcm.h"
 #include "clock.h"