lavfi/f_ebur128: relicense to LGPL

All copyright holders have agreed to the relicensing.
Approved-by: Andreas Cadhalpun <andreas.cadhalpun@googlemail.com>
Approved-by: David Sedacca <sedacca@comcast.net>
Approved-by: Ganesh Ajjanagadde <gajjanag@mit.edu>
Approved-by: Jean First <jeanfirst@gmail.com>
Approved-by: Kyle Swanson <k@ylo.ph>
Approved-by: Michael Niedermayer <michael@niedermayer.cc>
Approved-by: Nicolas George <george@nsup.org>
Approved-by: Paul B Mahol <onemda@gmail.com>
Approved-by: Thilo Borgmann <thilo.borgmann@mail.de>

LICENSE.md

@@ -26,7 +26,6 @@ Specifically, the GPL parts of FFmpeg are:
     - `tests/checkasm/*`
     - `tests/tiny_ssim.c`
 - the following filters in libavfilter:
-    - `f_ebur128.c`
     - `vf_blackframe.c`
     - `vf_boxblur.c`
     - `vf_colormatrix.c`

configure

@@ -3050,7 +3050,6 @@ cropdetect_filter_deps="gpl"
 delogo_filter_deps="gpl"
 deshake_filter_select="pixelutils"
 drawtext_filter_deps="libfreetype"
-ebur128_filter_deps="gpl"
 eq_filter_deps="gpl"
 fftfilt_filter_deps="avcodec"
 fftfilt_filter_select="rdft"

libavfilter/f_ebur128.c

@@ -3,19 +3,19 @@
  *
  * This file is part of FFmpeg.
  *
- * FFmpeg is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License along
- * with FFmpeg; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**