usb: gadget: function: uvc: fix sparse warnings

this patch fixes following sparse warnings:

uvc_video.c:283:5: warning: symbol 'uvcg_video_pump' was not declared. Should it be static?
uvc_video.c:342:5: warning: symbol 'uvcg_video_enable' was not declared. Should it be static?
uvc_video.c:381:5: warning: symbol 'uvcg_video_init' was not declared. Should it be static?

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/function/uvc_video.c

@@ -21,6 +21,7 @@
 
 #include "uvc.h"
 #include "uvc_queue.h"
+#include "uvc_video.h"
 
 /* --------------------------------------------------------------------------
  * Video codecs