package/libs/elfutils: fix license

package/libs/elfutils: fix license

elfutils libraries are not licensed under GPL-3.0-or-later, they are dual
licensed: GPL-2.0-or-later OR LGPL-3.0-or-later as clearly stated in
source files as well as on https://sourceware.org/elfutils:

The libraries and backends are dual GPLv2+/LGPLv3+. The utilities are GPLv3+.

Fixes: b98fb7664639a814f3dba309eaf38b62be137bb8 (elfutils: import package from packages.git)
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/19941
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>