usb: gadget: uvc: memory leak in uvcg_frame_make()

We need to add a kfree(h) on an error path.

Acked-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>