package/live555: license is now LGPL-3.0+ and not LGPL-2.1+

package/live555: license is now LGPL-3.0+ and not LGPL-2.1+

The live555 source code includes both a COPYING file (with the GPL-3.0
license text) and a COPYING.LESSER file (with the LGPL-3.0 license
text). However, all source files indicate a LGPL-3.0 license, and none
of them indicate a GPL-3.0 license. In addition,
http://live555.com/liveMedia/faq.html#copyright-and-license says the
source code is under the LGPL.

So, we:

- Bump LGPL License to 3.0+
- Add a comment about the GPL-3.0 license

Fixes:

- https://bugs.busybox.net/show_bug.cgi?id=13156

Signed-off-by: Michael Nosthoff <buildroot@heine.tech>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>