usb: gadget: uvc: Minimize #include in headers

In order to speed up compilation, only include the headers that are
strictly required within other headers. To that end, use forward
structure declaration and move #include statements to .c file as
appropriate.

While at it, sort headers alphabetically, and remove unneeded __KERNEL__
guards.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/uvc.h

@@ -9,16 +9,22 @@
 #ifndef _UVC_GADGET_H_
 #define _UVC_GADGET_H_
 
-#include <linux/usb.h>	/* For usb_endpoint_* */
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
 #include <linux/usb/composite.h>
-#include <linux/usb/gadget.h>
-#include <linux/usb/g_uvc.h>
 #include <linux/videodev2.h>
-#include <media/v4l2-fh.h>
+
 #include <media/v4l2-device.h>
+#include <media/v4l2-dev.h>
+#include <media/v4l2-fh.h>
 
 #include "uvc_queue.h"
 
+struct usb_ep;
+struct usb_request;
+struct uvc_descriptor_header;
+
 /* ------------------------------------------------------------------------
  * Debugging, printing and logging
  */