cam: kms_sink: Remove limitation that camera and display must match

There is a limitation that requires input and output to be pixel
for pixel identical in terms of height and width. Remove this
limitation to enable more hardware that doesn't match. Just start
drawing from top left 0, 0 corner.

Signed-o/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2020, Collabora Ltd.
 *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
 *
 * gstlibcamerapool.cpp - GStreamer Buffer Pool
 */

#include "gstlibcamerapool.h"

#include <libcamera/stream.h>

#include "gstlibcamera-utils.h"

using namespace libcamera;

enum {
	SIGNAL_BUFFER_