libcamera: proxy: Relicense proxy worker under LGPL

The proxy worker is licensed under the GPL. It is compiled as a binary
separate from libcamera.so, and it is our understanding and intent that
the GPL license doesn't propagate to libcamera.so. However, as the
worker is executed by libcamera.so, the GPL license may cause concerns
in this context, regardless of whether the concerns are valid or not.

This uncertainty could be addressed by a combination of a legal review
and an explicit intent clarification from the copyright holders. A
simpler option is to relicense the code under the LGPL.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Acked-by: Jacopo Mondi <jacopo@jmondi.org>
Acked-by: Paul Elder <paul.elder@ideasonboard.com>

src/libcamera/proxy/worker/ipa_proxy_linux_worker.cpp

@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
 /*
  * Copyright (C) 2019, Google Inc.
  *