ALSA: sound/usb/usx2y: fix sparse warning: Should it be static?

Impact: Move declaration to header file.

Fix this sparse warning:
  sound/usb/usx2y/usx2yhwdeppcm.c:739:5: warning: symbol 'usX2Y_hwdep_pcm_new' was not declared. Should it be static?
Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/usx2y/usX2Yhwdep.c

@@ -30,9 +30,6 @@
 #include "usbusx2y.h"
 #include "usX2Yhwdep.h"
 
-int usX2Y_hwdep_pcm_new(struct snd_card *card);
-
-
 static int snd_us428ctls_vm_fault(struct vm_area_struct *area,
 				  struct vm_fault *vmf)
 {

sound/usb/usx2y/usx2yhwdeppcm.h

@@ -18,3 +18,5 @@ struct snd_usX2Y_hwdep_pcm_shm {
 	volatile unsigned captured_iso_frames;
 	int capture_iso_start;
 };
+
+int usX2Y_hwdep_pcm_new(struct snd_card *card);