media: uvcvideo: Fix dereference of out-of-bound list iterator

Fixes the following coccinelle report:

drivers/media/usb/uvc/uvc_ctrl.c:1860:5-11:
ERROR: invalid reference to the index variable of the iterator on line 1854

by adding a boolean variable to check if the loop has found the

Found using - Coccinelle (http://coccinelle.lip6.fr)

[Replace cursor variable with bool found]
Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/uvc/uvc_ctrl.c

@@ -1844,30 +1844,35 @@ int uvc_xu_ctrl_query(struct uvc_video_chain *chain,
 {
 	struct uvc_entity *entity;
 	struct uvc_control *ctrl;
-	unsigned int i, found = 0;
+	unsigned int i;
+	bool found;
 	u32 reqflags;
 	u16 size;
 	u8 *data = NULL;
 	int ret;
 
 	/* Find the extension unit. */
+	found = false;
 	list_for_each_entry(entity, &chain->entities, chain) {
 		if (UVC_ENTITY_TYPE(entity) == UVC_VC_EXTENSION_UNIT &&
-		    entity->id == xqry->unit)
+		    entity->id == xqry->unit) {
+			found = true;
 			break;
+		}
 	}
 
-	if (entity->id != xqry->unit) {
+	if (!found) {
 		uvc_trace(UVC_TRACE_CONTROL, "Extension unit %u not found.\n",
 			xqry->unit);
 		return -ENOENT;
 	}
 
 	/* Find the control and perform delayed initialization if needed. */
+	found = false;
 	for (i = 0; i < entity->ncontrols; ++i) {
 		ctrl = &entity->controls[i];
 		if (ctrl->index == xqry->selector - 1) {
-			found = 1;
+			found = true;
 			break;
 		}
 	}